Talk:Centrifugal force/Archive 15

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Confusion with Centripetal Force

Without a doubt, many people come to this page to understand the difference between centripetal and centrifugal force. The current explanation, while correct, is only understandable to people who already understand these concepts. Here are two external articles that do a significantly better job: physlink.com and www.suite101.com/content/centripetal-vs-centrifugal-a15865 (can't link directly because of a spam filter, but the article is good). —Preceding unsigned comment added by 90.231.129.170 (talk) 01:52, 28 January 2011 (UTC)

Anon 90.231.129.170, It's a pity that such confusion should exist between two quite different concepts, particularly when the very etymologies of the two words mean that one is an inward acting force whereas that other is an outward acting force. And alot of that confusion is down to Isaac Newton. Have a look at this very interesting web link [1] which explains Newton's reaction to Leibniz's views on centrifugal force.

The two web links which you have provided are very much based on the Newtonian concept of centrifugal force being an equal and opposite reaction to centripetal force. But the truth is that centrifugal force is a pro-active inverse cube law force which is not in general equal in magnitude to the centripetal force. It is generally agreed nowadays that even in the special case of circular motion, where the centripetal force will indeed be equal in magnitude to the centrifugal force, that the two will not form an action-reaction pair. Also, in case you are in any doubt as to whether or not centrifugal force is a reactive force or a pro-active force, then consider the simple case of a weight being swung on the end of a string in a horizontal plane. The centripetal force is caused by the tension in the string. But that tension is first of all caused by the tendency of the weight to move in a straight line, which in turn causes the radially outward inertial effect. The inward centripetal force doesn't kick in until the centrifugal force is already established. David Tombe (talk) 17:04, 28 January 2011 (UTC)

Nonsense. Dicklyon (talk) 00:01, 29 January 2011 (UTC)

This does indeed seem nonsense. Yoenit (talk) 00:20, 29 January 2011 (UTC)

Yoenit, Can you please elaborate on what you are claiming is nonsense. Are you saying that Leibniz's equation,

${\ddot {r}}=-k/r^{2}+l^{2}/r^{3}$

is nonsense, and that you think that centrifugal force and centripetal force do constitute an action-reaction pair? Are you taking the Newtonian view?

Leibniz's point of view is essentially the same as Lagrange's point of view, and it is the point of view which appears in Goldstein's 'Classical Mechanics'. Centrifugal force is an outward inverse cube law force when angular momentum is conserved. It is therefore not in general equal to the inward gravitational force. In an elliptical planetary orbit, at perihelion, the centrifugal force will be greater than the centripetal force, and the planet will be accelerating outwards. The reverse is the case at aphelion. The two different power laws, as between inverse square law for gravity and inverse cube law for centrifugal force provide the orbital stability. I suggest that you read up a bit on celestial mechanics before you start making blanket criticisms as you have just done above. David Tombe (talk) 01:07, 29 January 2011 (UTC)

The Leibniz equation is not nonsense. It's just a special case of the standard interpretation as a fictitious force, for the case of a reference frame co-rotating about the point of the central forces on an object, for example rotating about the Sun to follow a planet under the influence of gravity. In the co-rotating frame, orbital motion is simplified to motion only along R, so it reduces to a 1D problem. As you say, the inward (gravitational) and outward (fictitious) forces are not balanced when ${\ddot {r}}$ is nonzero. Goldstein explains all this, as we've discussed before. Nothing wrong with it, just with your interpretation that "the truth is that centrifugal force is a pro-active inverse cube law force" and your statement that for the weight on a string "The inward centripetal force doesn't kick in until the centrifugal force is already established." If you want to imagine the centripetal force as an "effect", it is the effect of stretching the string by having the weight move is a straight-line path that takes it to greater distances; once the string stretches, it applies the centripetal force that accelerates the weight into a curving path; the reaction force to that is felt by the guy in the middle who is holding the string; it's this force that is part of a balanced pair: string tension pulls equally on both ends. That's the reactive centrifugal force; the fictitious force on the weight seen by a rotating observer is different, not part of a reaction pair; not a real force at all when viewed from an inertial frame, which is whey they call it fictitious. But you know all that, so why do keep up the nonsense? Dicklyon (talk) 02:36, 29 January 2011 (UTC)

Dick, I'm glad you agree that Leibniz's equation is not nonsense. You will see that in Leibniz's equation, centrifugal force is not reactive. And you will see that it obeys an inverse cube law. So why are you maintaining that my assertion that "centrifugal force is a pro-active inverse cube law force" is nonsnese?

As regards your analysis of the weight on the end of the string, you left out one important link in the chain of logic. We're agreed that the tendency of the weight to move in a straight line causes the string to become taut. But you left out the final clause "due to centrifugal force". The full sentence should read "the tendency of the weight to move in a straight line will induce a centrifugal force which will pull the string taut". And this centrifugal force is the very same centrifugal force which appears in Leibniz's equation. The tension in the string is a consequence which then causes a centripetal force to act. The linear analogy to this is a person accelerating in an elevator. The pro-active force is the downward gravity, and the reactive force is the upward normal reaction of the floor of the elevator, and the two are not an action-reaction pair because they are only equal in magnitude in the special case when the lift is not accelerating. David Tombe (talk) 11:19, 29 January 2011 (UTC)

Um, no. The weight moves in a straight line and causes the string to become taut due to the weight's inertia (and because someone is holding the other end of the string). To quote from the page before in the Swetz reference you mentioned above (with emphasis mine):

In the case of a body rotating in a circle on the end of a string (ideally outside a gravitation field, or shall we say on a frictionless horizontal table), there is only one real force, namely the tension in the string. And in the case of the comet, the only real force is the attraction.

Additionally, regarding Leibniz's centrifugal force, Swetz says on the page you linked to (with emphasis mine):

The question arises whether the earlier [Liebniz's] concept can be interpreted meaningfully. Considered as an endeavor of the circulating body, or a force acting on the body itself, it does not exist. But if we consider a reference frame fixed in the body and rotating with it, the body will appear to have an endeavor to recede from the centre. This of course is a fictitious force reflecting the acceleration for the reference frame.

In a stationary, inertial frame watching what goes on, Leibniz's term appears as a term in the inertial part, m*a, of Newton's 2nd law, not as a contribution to the net force acting on the object. In a linear analogy, the centrifugal force is akin to the downward endeavor/force that an occupant would say they feel as the elevator accelerates upward (or the upward endeavor/force felt as the elevator slow down). This isn't a real force, but, just like Swetz explains the Leibniz's centrifugal force, is really just a "fictitious force reflecting the acceleration for the reference frame". --FyzixFighter (talk) 15:09, 29 January 2011 (UTC)

FyzixFighter, The key point in your argument is that we are working under a set of rules in which what Swetz says, takes priority over what Leibniz himself has said. So let's then consider what Swetz has said. As regards the weight being swung around on the end of the string, you will agree that,

(1) The string is being pulled taut, and

(2) That Swetz says words to the extent that in a frame of reference fixed in the string, the weight will appear to have an endeavor to recede from the centre, and that this endeavor is a fictitious centrifugal force reflecting the acceleration of the frame of reference.

(3) That this fictitious centrifugal force, being a co-rotating example is equivalent to the inverse cube law centrifugal force in the Leibniz equation.

But somewhere along the lines, you are trying to argue that this centrifugal force is not the cause of the string being pulled taut. You are arguing that the string is being pulled taut by the inertia. Correct, it is indeed being pulled taut by the inertia. But the centrifugal force is the inertial effect in question, because as you already know, centrifugal force is an effect of inertia, and so the string is being pulled taut by an inertial centrifugal force.

On your second point, the person in the elevator feels real forces which are caused by the normal reaction of the floor of the elevator. The person in the elevator never feels the force of gravity. Likewise when a motorbike rider is riding inside an elliptical wall of death, he will only ever feel the inward acting centripetal force. But it is the outward acting centrifugal force which is pressing him into the wall in the first place. And this centrifugal force is not in general equal to the centripetal force. And the analogy with the elevator is that the normal reaction of the wall in the wall of death is analogous with the normal reaction of the floor of the elevator, while the centrifugal force in the wall of death is analogous to the gravitational force in the elevator. David Tombe (talk) 15:53, 29 January 2011 (UTC)

I agree with the anon who started this thread. This article does a bad job of explaining the concept to the general public because it s has become bogged down with spurious discussions on different types of centrifugal force. There is only one meaning of the term in current widespread use and that is the meaning that should be properly and clearly described here and sitinguished from centripetal force. I think a much tougher line on spurious nonsense is needed here. Martin Hogbin (talk) 16:00, 29 January 2011 (UTC)

Martin, the main meaning that you're referring to is in the article that moved long ago Centrifugal force (rotating reference frame). The present article Centrifugal force was created as a summary style article to cover briefly the relationship of that main standard meaning in physics to other uses of the term. We don't need to deny the other uses to get this right. Dicklyon (talk) 19:39, 29 January 2011 (UTC)

But the current situation is crazy. Someone who wants to know what centrifugal force is has to know that the meaning they want is Centrifugal force (rotating reference frame). This is like having USA(North America) and a summary page to distinguish it from USA(the name of my dog) and USA(small town in Mongovia) on it. The primary meaning should be the main article, all the other meanings are historical, specialist, or fringe. Martin Hogbin (talk) 20:12, 29 January 2011 (UTC)

No, I think that's nutty. A person who wants to know what it is will come here and learn that it can mean some different but closely related things. Then they can decide which meaning they're looking for and either read the short version or follow the main links to the long versions. I added a bit to the lead to lead into them a little better. Dicklyon (talk) 20:18, 29 January 2011 (UTC)

But it does not mean some different but closely related things, except in historical, (very dubious) specialist, or fringe (being polite) contexts. I have no objection to a section on these at the end of the article. I really do not understand your objection to getting this subject in proper order so that the article is helpful to readers, as the anon suggests. Martin Hogbin (talk) 20:26, 29 January 2011 (UTC)

Reactive CF is what? Fringe? Only historical? Specialist? I don't think so. Dicklyon (talk) 20:33, 29 January 2011 (UTC)

It is somewhat specialist or maybe just an idiosyncratic or outdated use of the term. Note also that even in that book it is given the name 'reactive centrifugal force' to distinguish it from plain 'centrifugal force'. I have no objection to a section on'Reactive centrifugal force' or 'Alternative meanings' but there is no doubt whatever that the main meaning of the term is the Centrifugal force (rotating reference frame). It is this sort of thing that confuses readers and brings WP into disrepute. There is only one meaning in current widespread use and it is our job to make this clear to people who do not know. Martin Hogbin (talk) 20:53, 29 January 2011 (UTC)

I disagree – there is considerable doubt. What you call "the main meaning" or the "only one meaning in current widespread use" is really the meaning within the physics community; that's "specialist" compared to the meaning to the general population of people who feel a tug on a string when they swing a weight around, or who want to know how a centrifugal clutch works. Why can't we treat these in a coherent and comparative way that helps people with one perspective understand both better? Dicklyon (talk) 21:06, 29 January 2011 (UTC)

Both the examples you give are best explained using the standard (physics) definition of CF. Reactive centrifugal force is a confusing concept when trying to explain why things happen, that is why the reactive definition has become less used over the last half-century or so, particularly in education. Martin Hogbin (talk) 22:50, 29 January 2011 (UTC)

And what is that one meaning in widespread use Martin? The force that stops the water falling out of a bucket when you swing it over your head? I'd also have no objection to a united article to cater for centripetal force too. Although centripetal force is quite different from centrifugal force, it does rather seem that alot of people get the two confused, and therefore one single article could explain all the issues in separate sections. There's a problem at centripetal force too. I used to think that centripetal force was a force which acts towards a centre, such as in the case of gravity in an orbit. But apparently there is a school of thought over at the centripetal force article which teaches it as being a force which acts act right angles to the direction of motion. The two definitions of course diverge once we move outside of circular motion and into elliptical motion. David Tombe (talk) 17:07, 29 January 2011 (UTC)

David, you have already admitted that your opinion on centrifugal force is based on there being a conspiracy amongst physicist to mislead people. That makes your views fringe, to say the least, and think you would do yourself a favour by withdrawing from discussion of this subject. Martin Hogbin (talk) 18:36, 29 January 2011 (UTC)

Martin, I don't recall ever saying that my opinion on centrifugal force is based on there being a conspiracy amongst physicists to mislead people. My opinion on centrifugal force is the same as that of Leibniz and Maxwell, and I arrived at my conclusions from studying planetary orbital theory in Goldstein's 'Classical Mechanics'. Rather than anybody withdrawing from the discussion, it would be much more helpful if you would actually engage in the discussion. I want to see some evidence that you understand the topic. David Tombe (talk) 19:01, 29 January 2011 (UTC)

Maybe that is because you deleted it from your talk page. You said,'The only reason why anybody might oppose such a planetary orbital section is for ideological reasons. For example it might clash with a mindset based on relativism where everything is relative and in which there are no absolutes.' Martin Hogbin (talk) 20:22, 29 January 2011 (UTC)

Martin, I said that further up this talk page. It might be archived now. I was trying to speculate on why such an established topic was meeting with such strenuous resistance. David Tombe (talk) 21:44, 29 January 2011 (UTC)

Centrifugal force in engineering

There seems to be a suggestion here that engineers usually use the term 'centrifugal force' to refer to the reaction to the centripetal force and that this is desirable or necessary for the convenient understanding of things like centrifugal pumps, centrifugal clutches and stresses in turbine blades. I see little evidence that this is the case.

Consider a drawing of, say, a turbine blade with stresses and centrifugal forces marked on it. The engineer may consider the marked forces to be the reaction forces. On the other hand, they may well be considering themselves to be working in a frame of reference that is rotating with the blade, after all the blade does not rotate on the paper (or screen). If that is their understanding of what they are doing (and they probably have more important things to do that consider that subject in detail) then there is no problem with the marked forces being the standard inertial (I much prefer that term to' fictitious') forces that exist in a rotating reference frame.

Similarly, in the case of a centrifugal pump, it seems quite natural to use a reference frame rotating with the impeller, thus the water is pulled outwards by centrifugal force. Simple.

One case I can see where this approach is not so natural is that of water flowing round a curved pipe. Here the non-rotating frame of the pipe is the natural one. Martin Hogbin (talk) 10:55, 30 January 2011 (UTC)

Martin, if we are treating 'reactive centrifugal force' as a kind of 'apparent weight' concept, then a distinction does become relevant in non-circular motion. The 'reactive centrifugal force' will not in general be equal to the pure inertial force that causes it. The 'reactive centrifugal force' will always equate to the centripetal force, where such centripetal force has been induced by an inertial centrifugal force causing an object to press or pull against another object. See the comments below. David Tombe (talk) 14:17, 30 January 2011 (UTC)

The latest edits

Dick, Regarding your new paragraph, would it not have been better if you had said that these situations can be analyzed using either the 'rotating frames' approach or the Lagrangian approach, and in the special cases where circular motion is involved, the centrifugal force will be equal in magnitude to the centripetal force, and so we can used the 'reactive centrifugal force' approach? David Tombe (talk) 21:44, 29 January 2011 (UTC)

I think the Lagrangian approach is way too specialist to even mention at that point. Both approaches mentioned can be used, whether the motion is circular or not. Dicklyon (talk) 21:56, 29 January 2011 (UTC)

Dick, The reactive centrifugal force concept can only be used when the centrifugal force and the centripetal force are of equal magnitude. That is one of the reasons why I object to it. It seems that you have got confused about an already faulty concept. I don't think that the last lines of your new paragraph are very clear. Do you think the readers will get your point about these different centrifugal forces are not equal in general, especially when radial acceleration is involved? Also, where does the reactive centrifugal force enter the picture for somebody tied to an aeroplane propeller with the rotation origin right in their middle? David Tombe (talk) 23:47, 29 January 2011 (UTC)

When the reactive centrifugal force concept is used, it's equal ``by definition to the centripetal force, which is defined in terms of a center of osculation. It doesn't matter whether the motion is circular or not. I agree that "especially when radial acceleration is involved" is probably only going to confuse; I'll take it out. Dicklyon (talk) 00:41, 30 January 2011 (UTC)

Dick, If the two are equal I can't see how it wouldn't be circular motion. Anyway, what is meant by your statement these different centrifugal forces are not equal in general? Can you give me a scenario where they aren't equal. David Tombe (talk) 01:08, 30 January 2011 (UTC)

Consider a centrifugal railway with a non-circular loop. At each point, the centripetal force provided by the track is equal to the reaction force on the track by the rail car. If you need to resolve the forces to get rid of non-centripetal components, it's still true. Dicklyon (talk) 02:11, 30 January 2011 (UTC)

Dick, I've got your point, but you need to think very carefully about this. The non-circular situation which you have given is analogous to a person accelerating in an elevator. When the elevator is accelerating downwards, the force of gravity will be unaltered, but the upward normal reaction of the floor will be reduced. The person feels lighter because the upward normal reaction from the floor is less. Likewise in an elliptical centrifugal train, the centripetal force will be less as the train is moving further from the centre. But the centrifugal force as per the Leibniz equation, or as per the rotating frames approach, will still be calculated in the normal way.

But I can see that you are looking at the actual outward physical push on the floor of the train, and this will certainly be less than in the circular motion case if the train is moving outwards from the centre. It is this physical push which induces the inward centripetal force. I assume that it is this effect which you are taking to be the 'reactive centrifugal force'? And what would the equivalent be in the elevator? The person's weight doesn't change, but the degree to which gravity causes them to push against the floor does change as the elevator accelerates. We would tend to use the term 'apparent weight' for that situation, and so I suppose that your concept of reactive centrifugal force would bear an analogy with the concept of 'apparent weight'.

But is that what Newton had in mind for 'reactive centrifugal force'? Newton invoked the concept in relation to the Leibniz's planetary orbital equation, and in that situation we are not dealing with circumstances in which centrifugal force causes an object to press or to pull against another object such as to induce a centripetal force. In planetary orbits, the centripetal force is pro-active, so I'm not sure if your concept of reactive centrifugal force is the same as Newton's concept of reactive centrifugal force. Having said that, I think that Newton's concept of reactive centrifugal force in connection with planetary orbits was quite wrong. Your concept on the other hand, despite being driven by a pro-active centrifugal force, is in many ways a reactive concept. The centrifugal force pushes the person against the floor. The centripetal force then arises as a shared reaction between the person and the floor, and that's what gives the apparent weight.

This subject needs to be better explained in the article, and it definitely requires a section of its own. I don't think the readers are going to grasp what you mean by the centrifugal forces not being equal in general, unless there is some kind of demonstration such as the one you have mentioned about the centrifugal railway. Best to leave that line out of the introduction. David Tombe (talk) 14:07, 30 January 2011 (UTC)

I'll stay out of it for a while and see if others come up with a better lead or more explanation. Dicklyon (talk) 21:26, 30 January 2011 (UTC)

Dick, Likewise, I'll stay out of it for a while too and watch what other editors can suggest. But I do think that I have identified the 'reactive centrifugal force' as being an analogy with 'apparent weight'. And of course, apparent weight is not equal in general to the force of gravity. Apparent weight is only numerically equal to the force of gravity when the reaction surface is not accelerating towards or away from the object in question. For a better understanding of this subject in general, we might think about dividing examples into three categories,

(1) Examples involving centrifugal force in conjunction with push and pull interactions with strings, springs, and floors, which cause a centripetal force.

(2) The linear analogies to the above involving gravity in conjunction with push and pull interactions with strings, springs, and floors, which cause tensions and normal reactions. The accelerating elevator will give good analogies with elliptical motion at (1).

(3) Examples in which gravity and centrifugal force come face to face without any involvement of push or pull interactions. This is where the Leibniz equation comes in, pitting the inward inverse square law gravity force against the outward inverse cube law centrifugal force such as to lead to elliptical, hyperbolic, or parabolic orbits. David Tombe (talk) 22:28, 30 January 2011 (UTC)

Layman's terms

Can someone add an English version? Seriously, way too technical for a Wikipedia entry from paragraph one. --66.119.170.242 (talk) 00:53, 29 January 2011 (UTC)

I have to agree, this article starts with a confusion and then adds to it. I cannot see why we have to dive into rotating coordinates and the awful term fictional forces. In everyday fixed coordinates where we observe things as rotating, like a roulette wheel, there is a real force, in this case exerted by the ball on the constraining rim. Of course this is a real force experienced by the rim and it is equal and opposite to the centripetal force on the ball and of course we understand this force is rotating as we watch.Profstandwellback (talk) 17:33, 31 January 2011 (UTC)

Profstandwellback, I brought your comments down to here in order to better reflect the chronology of posting. Anyway, what you have just said is more or less what I have been saying all along. The subject can mostly be explained without recourse to mathematics. Even in the case where centrifugal force comes face to face with gravity in a planetary orbit, we could simply write in plain English that gravity is an inward inverse square law force and that centrifugal force is an outward inverse cube law force and that the combined effect leads to orbits which are circular, elliptical, parabolic, or hyperbolic. David Tombe (talk) 19:11, 31 January 2011 (UTC)

@Profstandwellback - what you're describing is the reactive centrifugal force, a force that the ball exerts on the constraining rim in accordance with Newton's 3rd law. It always exists (though in some cases it might not technically be "centrifugal") independent of the frame of the observer. The inertial/fictitious/pseudo/however-you-want-to-call-it force is a force that appears to be exerted on the ball - it only appears to exist inside a rotating frame, is determined by the rotation rate of the frame, has no third law partner, and is only an illusion of a force. In the inertial (stationary) frame there is no such force (force as defined in classical Newtonian mechanics, anything that contributes to F_net in Newton's 2nd law). I'd reccommend Roche's article "Introducing motion in a circle" which I think does a pretty good job of distinguishing the two. --FyzixFighter (talk) 00:02, 1 February 2011 (UTC)

In reply to FyzixFighter, I think I understand where you are coming from but it makes the simple seem complicated. Force is a real thing, it can be experienced by an observer or by an object , it can be felt as a real pressure (force divided by area), it can break real objects etc so why call it a fictional force? We can explain that it arises by the continual radial acceleration of a rotating object, which is a real acceleration inside our "normal" frame of reference. Students may find a continual acceleration hard to grasp when compared with a linear acceleration but it is sure to baffle them if you switch to rotating coordinates, a difficult intellectual leap, and then say the force is fictional. If you are inside the rotating frame, say on a fairground ride, you experience a very real force do you not? To call it fictional in order to use clever mathematics is perverse. Centrifugal force is simply the opposite of centripetal force, it is a real everyday force and simple to calculate from the angular rate. You can go on to explore the effects of alternate frames of reference for more advanced students, but Occams Razor tells us to choose the simpler explanation over the complex.Profstandwellback (talk) 14:00, 1 February 2011 (UTC) Can I dare to add a question about the point of WP? Is it to provide instruction to students? In which case we must at each step take the student from what they already understand to a new a deeper understanding. Therefore we begin with common everyday experience such as swinging a ball on a string and stuff like that. The forces involved need to be compared to other forces such as weight (this is a major step in understanding the world) and related to the origin of forces such as gravity and acceleration. The centrifugal/centripetal chestnut should not be allowed to become folklore like the story that "the bee can't really fly but no-one told him." When there is both rotation and radial acceleration or angular acceleration, the picture is significantly more complex and there is no hope of reaching understanding unless you have first grasped simple rotation examples. It is a huge mistake to approach the subject through maths rather than experience because this will turn many students off for life when a simple step by step explanation will bring those "AHA' moments. If WP is to have esoteric discussion about frames of reference, then fire away but don't expect to get converts from the people who are curious to understand but missed meeting Newton, I gather he was not a good teacher, just a cranky genius, there is a role for simple teaching.Profstandwellback (talk) 14:30, 1 February 2011 (UTC)

The goal of WP is to present what is verifiable, that is, what appears in reliable sources. I think there is a distinction, perhaps subtle, between it being a textbook (which it should not be) and it being an encyclopedia. One endeavors to teach while the other endeavors to inform. Again, I suggest if possible that you read the Roche article which sums up the other reliable sources and explains the two main and distinct uses of the term "centrifugal force" in science. Simple is good, but not if it makes something wrong. Let me be clear that I am not happy with the current state of the articles and that I feel that something could be done to clear up confusion, such as a merger, and I do feel that, when possible, a simple explanation should precede a mathematical derivation.

The term "fictitious" only applies to the centrifugal force that appears in rotating frames - reactive centrifugal force is very real and arises whenever you have a contact or binding centripetal force. Let me try an example to distinguish the two. A passenger is in a vehicle in the seat but not touching the wall yet and the vehicle rounds a corner. The passenger will say that she feels a force pushing her outward, and in fact relative to the seat she does accelerate outward until she meets the wall of the vehicle. So here are the two centrifugal forces: 1) from the perspective of the passenger, she feels a force exerted on her pushing her outwards, and 2) she exerts a centrifugal force on the wall when she reaches it (and the wall exerts a centripetal force on her). Now according to the passenger, there are three forces - two acting on her and one that she exerts on the wall. However, a stationary observer does not see the first one but merely sees the passenger moving in a straight line, and the vehicle and the seat moving out from under her until she comes into contact with the wall, at which point the contact force from the wall accelerates the passenger inward so that she follows a curved path. The stationary observer see only two forces - one that the wall exerts on the passenger and one that the passenger exerts on the wall. According to the stationary observer, what passenger perceives as an outward force on her is an illusion caused by her using the vehicle as her reference frame and neglecting to account for the frame's acceleration. In this example, the first centrifugal force is the typical usage of the phrase in modern physics. There are occurrences of the second, and the term centrifugal force does rightly apply to that force, but it is distinct form the first when you consider what the two forces are acting upon and whether the force is part of F_net in Newton's 2nd law in the inertial frame. Again, these are the uses as found in reliable sources. We can probably do better in giving a layman's explanation, but we should not sacrifice accurately relaying the information in reliable sources for the sake of perceived simplicity. --FyzixFighter (talk) 15:22, 1 February 2011 (UTC).

Thank you for a long explanation. I think a textbook and an encyclopedia share a didactic purpose and should still progress from sim ple to complex. I think the following is simple and rigorous, based on Newton. If a massive particle is constrained to rotate in a circle it will exert an outward radial force on the constraint. This is called centrifugal force. It is a real force with value found by multiplying the mass by the radius and by the square of the angular velocity. It remains the same value in rotating coordinates but the vector rotation can and must be reinterpreted. The constraint can take several forms (as has been discussed in previous posts). If the particle is constrained into a circular path with changing radius an interesting force is required acting at right angles to the trajectory called the Coriolis force. This is also a real force and very important in understanding many phemonena. Centrifugal force and Coriolis force along with Euler and gyroscopic forces can be called inertial forces because they arise from constraining a mass to follow any general path which is not a straight line. (Newtons first law) The constrained mass particle in the simple case of a circle experiences an inward radial force called the centripetal force which in this simple case is equal and opposite to the centrifugal force. Once the case is complex (non circular) the inertial forces cross couple depending on the three dimensional form of the constraint. This situation obtains in many real life examples as have been discussed as engineering examples.Profstandwellback (talk) 11:28, 2 February 2011 (UTC)

(I hope you don't mind me modifying the indenting to keep this a bet separate from the other discussion below) Again, what you're describing is the reactive centrifugal force and is not the way that the term is typically used in physics (when analyzing the motion of an object, I generally don't care about the forces that the object exerts on it's surroundings), nor how the lay person generally thinks about centrifugal force. I think that the lay person generally thinks about centrifugal force as the apparent force that pushes an object outwards in rotating frame, and not the force that the object exerts on a wall. Let me try another example, the Rotor (ride). People will usually say that it is the centrifugal force pushing them against the wall, but such a force is an illusion according to an inertial observer. There is an outward centrifugal force that the person exerts on the wall, but that is not the typical physics usage of the term and I don't think that the lay person is talking about that force when they use the term. Additionally, if people in the Rotor start throwing objects around, they will note that, from their perspective, objects follow curved paths and do not appear to obey Newton's 2nd law. In order to make Newton's 2nd law work from their perspective they must include the centrifugal force and the Coriolis force. These are the typical "fictitious" forces of physics, since to an inertial observer the objects do obey Newton's 2nd without invoking the apparent forces. Also note that there are no "constraining" forces for these objects so no reactive forces, so the usage of the concepts of centrifugal force and Coriolis force to describe their motion within the rotating frame is clearly distinct from the concept of reactive forces.

As I mentioned before, there are references that talk about the reactive centrifugal force, generally engineering sources talking about internal stress in solid rotating objects, which is distinct from how the term is generally used in physics. I don't think I have ever seen in any source how you've used the terms Coriolis force and Euler force. I have only ever seen those used for the apparent ("fictitious" or inertial) forces that arise from frame rotation and that are exerted on an object, not to describe the force exerted by the object on it's constraint. If you haven't yet read the Roche reference in the Physics Eduction journal, I highly recommend it because it does come at the concept from a pedagogical perspective. --FyzixFighter (talk) 15:23, 2 February 2011 (UTC)

thank you for the above argument, I think we agree that centripetal is the force on the particle while centrifugal is the force on the constraint and I agree the layman needs to be shown that centrifugal F. is not the force on the rotating mass. However I think the layman also appreciates that if you power up the rotation speed eventually the centrifugal forces will break the constraint, often dramatically in many engineering examples so she will be confused to be told the centrifugal force is imaginary or fictional. I appreciate the physics concentration on the trajectories of particles but in many engineering cases the forces on the constraints are important. So could we agree that the early part of the description in this article should clarify that the centrifugal force acts on the constraint in rotating systems with the usual examples and the maths treatment can be left till a later paragraph?Profstandwellback (talk) 14:57, 3 February 2011 (UTC)91.125.59.10 (talk) 14:35, 3 February 2011 (UTC)

The reactive centrifugal force is already mentioned in the first paragraph of the lead as one of the uses, and it is summarized in the third subsection, in about the same amount of space as the "fictitious" centrifugal force in the subsection above it. However the main usage of the term is in the context of rotating frames so, imo according to WP:UNDUE, that should be the position given the greatest emphasis. The reactive force has only limited usage and is not the common usage of the term, even if you or I or anyone else thinks that it should be (for the record, I don't) - the fact of the matter is that most reliable sources use "centrifugal force" to refer to the pseudo-force in rotating frames. We can and do mention both uses and should explain the difference between the two, but we should not try to "right great wrongs" by reversing the emphasis found in reliable sources and in mainstream science. --FyzixFighter (talk) 15:08, 3 February 2011 (UTC)

Gee. Gosh darn it. Just as soon as someone who knows what he is talking about begins to made a important and useful contribution to eliminating the idiotic nonsense of Wikipedia speak, along comes one of the lead fools, and tries to run the guy off. I suggest that you ignore this guy FyzixFighter, he is a know obstructionist, and get on with making some really needed changes to this article, so that really intelligent people can make sense of it. As it stands now, only those who speak physics nonsense can make sense of it. That may be rough going for you Prof Stand Well back, but it needs to be done. I hope sanity prevails since that is certainly absent in Wikipedia. —Preceding unsigned comment added by 72.64.47.126 (talk) 00:30, 1 February 2011 (UTC) —Preceding unsigned comment added by 72.64.51.3 (talk)

Quite the reverse. The use of the term 'centrifugal force' outside if its meaning as an inertail force in a rotating reference frame has proved so utterly confusing that it has been generally agreed that it is best not to use the term at all except in that context. If you work in an inertial reference frame there is no need for centrifugal force of any kind. Martin Hogbin (talk) 19:08, 1 February 2011 (UTC)

Hey double talk is what needs to be cleared up. You are not helping that effort. The idea of centrifugal force was pretty clear until physicists mucked it up. I dont see any clarity here that helps to explain it.72.64.51.3 (talk) 19:32, 1 February 2011 (UTC)

There is no need to use the term at all when working in an inertial frame. That seems simple enough to me. Martin Hogbin (talk) 19:37, 1 February 2011 (UTC)

Are you then saying that there's a need to deny that people do use the term to describe forces felt in an inertial frame, like the tug on the string that you're whirling around? Even some physics books have been pointed out that use it that way, so why should we go out of our way to pretend otherwise? Dicklyon (talk) 01:04, 2 February 2011 (UTC)

If some sources say that the term is sometimes used to describe the reaction to the centripetal force that we cannot deny that fact but I think to put that usage on equal terms with the inertial force would be giving undue weight to what is, I believe, an obsolete usage for physicists and engineers alike. The use of the term for a reaction force is spectacularly unhelpful in understanding the subject and is the cause of much confusion, probably including some on this talk page. The gist of one of the sources used to support that usage is that it is best not to use the term at all at an elementary level, something that I agree with. In other words there is not need to use the term when working in an inertial frame and no benefit from doing so. It is only when the more advanced subject of rotating frames is introduced that we need to introduce the term, or to put it another way, if you do not understand the inertial force necessitated by virtue applying Newton's laws unchanged in a rotating frame then it is best not to use the term at all. Martin Hogbin (talk) 22:49, 2 February 2011 (UTC)

I do have some sympathy for your POV about how people should use the term, like physicists do use it. But this section started by someone asking for an explanation in "layman's terms"; and laymen do use the term and do have explanations involving it; they talk about at outward force, and they do it without "rotating reference frames". I'm not asking to put it "on equal terms", but on reasonable terms at least. Dicklyon (talk) 04:39, 3 February 2011 (UTC)

Do laymen use the term without reference to rotating frames? I think that much of the time they are not quite sure what reference frame they are using. I have no objection to mentioning alternative uses of the term but I doubt very much that this will help laymen understand anything. The best advice to a layman or beginner is not to use the term at all if you want to understand what is going on. Martin Hogbin (talk) 00:04, 4 February 2011 (UTC)

can I refer you to my conversation a few paragraphs above?Profstandwellback (talk) 14:57, 3 February 2011 (UTC)91.125.59.10 (talk) 14:42, 3 February 2011 (UTC)91.125.59.10 (talk) 14:39, 3 February 2011 (UTC)

The problem with using the term 'centrifugal force' to refer to the reaction force on a constraint is that it gives no clue is to where the this mysterious force comes from. It is the reaction to the centripetal force so why not just call it this, no special name is needed, we do not have special names for the reaction to Coriolis force, for example. Martin Hogbin (talk) 00:04, 4 February 2011 (UTC)

Martin, In reactive situations, centripetal force only arises because a centrifugal force is either pulling on a string or a spring, or pushing on a surface. The centripetal force is not the prime mover in the situation. And so you ask where does this mysterious centrifugal force come from? It comes from physical inertia. As regards reactions to a Coriolis force, I can't imagine that within the context of your notion of a fictitious Coriolis force that there would ever be a reaction to one. You need to find a real Coriolis force where inertia is involved, and then you'll see how it reacts with constraints. David Tombe (talk) 00:41, 4 February 2011 (UTC)

FyzixFighter, I notice above that you are acknowledging the existence of the actual outward push against a constraining surface. But then you are making the disclaimer that this is merely 'reactive centrifugal force'. But you are overlooking the fact that this 'reactive centrifugal force' is actually caused by 'centrifugal force'. And the centrifugal force which causes it exists independently, whether or not we have a reaction with a string, spring, or surface. Have a look at this card here which you will find at number 12 in this web link [2]. Imagine that you are an observer standing on the tarmac. You will be in an inertial frame of reference. When the propeller spins, all the liquid and softer tissues inside Robin will move radially outwards from his middle. No centripetal force is involved in the destructive mechanism. This is a display of pure centrifugal force as observed from an inertial frame of reference, and it is very real. It will destroy Robin. And Robin can't make the smart remark which James Bond made in the other cartoon about the destructive effect being attributable to centripetal force. The centrifugal force alone is what will be destroying Robin in this case scenario. David Tombe (talk) 16:17, 2 February 2011 (UTC)

Nonsense. What's making Robin's body parts follow a curve path if there's no centripetal force? Dicklyon (talk) 17:46, 2 February 2011 (UTC)

Dick, Centripetal force will make a vain attempt to hold Robin together, but the damage will all be done by pure centrifugal force. I should have specified in the paragraph above that I was referring to centripetal force in relation to its absence in respect of the destructive mechanism. I have now corrected that.

In the James Bond cartoon however, the centrifugal force is pushing Bond against the rim, and so centripetal force is involved in the destructive mechanism. The Batman cartoon is an example of pure centrifugal force which doesn't involve a reaction, whereas the James Bond cartoon is an example of centrifugal force in which a reaction surface is involved. David Tombe (talk) 18:41, 2 February 2011 (UTC)

Nonsense. Dicklyon (talk) 04:39, 3 February 2011 (UTC)

Dick, Your response indicates that you have got no argument. The James Bond cartoon, which is here, [3], shows James Bond being pushed against the rim by centrifugal force. Centripetal force will then counteract the centrifugal force, and Bond will be crushed by the sandwich effect. Bond claims that only centripetal force is involved. However, put Bond into the position that Robin is in in this Batman cartoon at card 12 here [4] and Bond will not be able to use the argument about centripetal force. The destruction will be caused entirely by centrifugal force, because the centripetal force will be insufficient to hold Robin together. In fact if we were to watch three people in a row, each tied to a propeller, just like Robin, it would be a perfect triple display of centrifugal force as viewed from an inertial frame of reference. We would see centrifugal force radiating out from three centres. It would be very difficult to actually view the centrifugal force in this context from a single rotating frame of reference, because we wouldn't know which propeller to co-rotate from. David Tombe (talk) 12:54, 3 February 2011 (UTC)

Can I add yet another example? In conversation with FyzixFighter above, we agree that centripetal is the force on the rotating particle while centrifugal is the force on the constraint (which is forcing the particle into rotation). In many examples it is confusing which is which. Consider a spin drier, the drum is spinning but is also the constraint. The wet clothes rotate because of centripetal force but the water leaves the drum. We know the instantaneous motion of the water drops is tangential but that also looks like radial to a casual observer, no wonder people get confused. The water leaving is not fictional nor centripetal it is expelled by its inertia and until it breaks free of the drum we can call the force centrifugal.Profstandwellback (talk) 14:57, 3 February 2011 (UTC)91.125.59.10 (talk) 14:54, 3 February 2011 (UTC)

Prof, the case you give above is an excellent example of the confusion that arises from the misuse of the term 'centrifugal force'. In the non-rotating frame, the 'centrifugal force' acting radially outwards somehow makes the water leave tangentially?? Far better to say that the water continues its motion in a straight line but the drum moves round in a circle, thus the water leaves the drum. On the other hand, in a frame rotating with the drum, the radially acting centrifugal force makes the water leave radially. Perfectly logical. Martin Hogbin (talk) 00:04, 4 February 2011 (UTC)

Profstandwellback, Yes, the spin drier example is another example in which the centrifugal force flings the stuff outwards without being hindered by an inward centripetal force. In the James Bond cartoon, the normal reaction of the rim and the friction on the rim would be called dragging forces since they cause the object to co-rotate with the system. In the spin drier, we do have a transverse dragging force, but since we have no inward radial dragging force (ie. no centripetal force), then the outward centrifugal force prevails, and the water flies outwards beyond the rotating drum.

And in relation to what you said about it flying off tangentially, but that it looks as if it is flying off radially, it is actually doing both simultaneously. And that reminds me that there is a gaping ommission in this article. There is no section on 'centrifugal potential energy'. If we swing a weight in a vertical plane to a very high angular speed and then release it under arm, it will fly away an enormus distance. This will represent an huge radial expansion from the rotation origin. The tangential aspect will pale into insignificant. This is a classic display of centrifugal potential energy being unleashed. There used to be a section about this including the mathematical formula for centrifugal potential energy but it seems to have gone. David Tombe (talk) 17:27, 3 February 2011 (UTC)

My only argument is that if you don't back up your approaches with reliable sources, they are essentially nonsensical. David likes to point to Goldstein, but ignores what Goldstein says about how he got to the radial equation via a co-rotating system. There are no outward forces on the particles of water, and no radial motion of the particles away from the spinning drum, unless you are looking at it in a rotating system. The only outward forces in an inertial frame are on the "constraints"; these are the reactive centrifugal force. These are the only two interpretations I've seen in sources. Dicklyon (talk) 23:30, 3 February 2011 (UTC)

Dick, Goldstein doesn't mention rotating frames of reference in connection with planetary orbits. At least not in the 1950 and 1980 editions which are the editions which he personally wrote. And planetary orbits don't involve constraints. They involve centrifugal force coming face to face with gravity. Angular momentum will be conserved and the centrifugal force will obey an inverse cube law. In other situations where centrifugal force does get involved with constraints, then there will of course be a reaction which can be physically felt, but there is no reason to have this reaction dealt with in a separate article as we are doing at the moment. And if a centrifugal force breaks through any constraints, it will still be that same centrifugal force as in the planetray orbital equation. The object will continue in a straight line and it will have a constant angular momentum relative to the origin, and the radial expansion will obey the inverse cube law. The motion will be both radial and transverse to the origin, and there will still be inertia which will be felt as soon as any new constraint is put in its path. David Tombe (talk) 00:14, 4 February 2011 (UTC)

Martin, Regarding your reply to Profstandwellback, he didn't say that the centrifugal force makes the water leave tangentially. He said that it leaves tangentially. The tangential motion is due to the already existing tangential motion. This tangential motion causes a centrifugal force which deflects the tangential motion into the radial direction. The object flies outwards with both radial and tangential components of motion, and the tangential motion is constantly deflecting into the radial direction. Eventually the radial motion will become dominant. David Tombe (talk) 00:24, 4 February 2011 (UTC)

David, your erroneous assertion that "Goldstein doesn't mention rotating frames of reference in connection with planetary orbits" was answered in detail back in '09, here. Dicklyon (talk) 04:25, 5 February 2011 (UTC)

Reactive centrifugal force as a helpful concept

To respond to several replies above I ask anyone to give me an example where specifically naming the reaction to the centripetal force 'centrifugal force' is a helpful concept. Martin Hogbin (talk) 09:28, 4 February 2011 (UTC)

Martin, The reaction to a centripetal force is a particular manifestation of centrifugal force which can be physically felt. This article is about centrifugal force and therefore that manifestation needs to be dealt with in the article, as does 'centrifugal potential energy'. But the reaction to a centripetal (constraining) force is not the only manifestation of centrifugal force. Centrifugal force in general can be plotted mathematically by constructing Newton's laws in a rotating system and it will show up in any straight line motion relative to any arbitrarily chosen origin. And even when there are no radial constraining forces (radial dragging forces) involved, there are situations in which centrifugal force can still be physically felt and observed. Consider three propeller driven aircraft sitting on the tarmac. Tied to the three propellers are the Joker, the Riddler, and the Penguin. When the propellers are going full power, these three men will explode. Their molecules will accelerate radially outwards in all directions. We will witness three explosions from three epicentres and we will be standing in an inertial frame of reference. Is this a display of centrifugal force, or is it a display of the fact that particles continue to move in a straight line unless acted upon by a force? David Tombe (talk) 11:14, 4 February 2011 (UTC)

I was rather hoping that someone would try to give an example where the use of the concept of reactive centrifugal force was helpful in understanding some phenomenon, process, or equipment. How does that concept help explain your scenario? Martin Hogbin (talk) 12:11, 4 February 2011 (UTC)

Maybe this is an example; in a shell fuse there is a need for a timing and arming function to prevent the fuse being live until it has left the barrel. One method is to have ball bearings on a ramp constrained to move radially against a spring. The shell is spun during acceleration and the balls move outwards under centrifugal force, compressing the spring until it latches in the armed position. Another: in a rock crushing machine, rocks are dropped into a rotating drum with vanes which encourage the rocks to accelerate radially rather like a water pump. The lining of the drum is either hard or tough and the centrifugal energy smashes the rocks. In a conical pendulum governer, the weight(s) are constrained to move radially and reach an equilibrium displacement. The weights are centripetally constrained by gravity but the mechanism operated by the weights experiences centrifugal force.Profstandwellback (talk) 12:44, 4 February 2011 (UTC)

In a so called centrifugal clutch a set of friction pads lines a drum, held from contact by springs. When rotating the friction pads move radially outwards and exert a couple on the drum causing it to rotate; when the rotation is fast enough the pads and drum become locked together by friction caused by the high centrifugal force (and of course the corresponding centripetal force.)Profstandwellback (talk) 12:51, 4 February 2011 (UTC)

In another example from history, in about 1971 Rolls Royce (Aero engines) introduced carbon fibre turbine or compressor blades. Unfortunately the blades suffered radial creep due to centrifugal force and this problem after a while brought the company to insolvency; perhaps the most prominent case of corporate collapse due to centrifugal force ever recorded.Profstandwellback (talk) 13:03, 4 February 2011 (UTC)

Prof, your examples are just ones in which the term 'centrifugal force' is used in a casual way without specifying any reference frame. What makes the turbine blades creep? Centrifugal force. That is absolutely fine, I might have in mind an inertial force in the reference frame rotating with the blade and a layman probably will not have thought to consider the need for a reference frame at all. I have no objection to mentioning the informal use of the term to generally describe the force that pulls things outwards when you whirl them around, although I would point out that this terminology is now strongly discouraged as being confusing. It is fine for someone with no technical understanding or interest but for a budding engineer or physicist is is better not to use the term at all as it will sow the seeds of confusion that have blossomed all over this article.

What confuses things even more than the casual use of the term is the attempt to justify this by applying the term 'centrifugal force' to an outward going reaction to the centripetal force. That reaction force is just like any other reaction force, giving it a special name that is actually needed to describe a different concept helps no one. Martin Hogbin (talk) 13:43, 4 February 2011 (UTC)

Martin, The so-called 'reactive centrifugal force' is caused by centrifugal force. 'Reactive centrifugal force' stands in the same relationship to inertial centrifugal force, as apparent weight stands to gravity. But I have never approved of the name 'reactive centrifugal force', because in the situations where it is used, it is actually the inward centripetal force which is the reaction. The centripetal force can be a consequence of the pressure which a wall of death rider applies to the surface, or it can be a consequence of the tension which a swinging weight applies to the spring or the string. Either way, we need a primary centrifugal pressure to kick off the reaction.

I don't want to have a special article for reactive centrifugal force. I want those case scenarios dealt with in this article, with reference to non-circular scenarios such as the centrifugal train. And you still keep overlooking the fact that in celestial mechanics, we deal with pure inertial centrifugal force in a radial gravitational field in which no physical reaction is felt. Centrifugal force is a single topic, and the reason why it has been fragmented into so many articles has been due to a lack of comprehension of the topic on the part of those who fragmented it into five different articles. David Tombe (talk) 14:27, 4 February 2011 (UTC)

I do not want to confuse anybody. I agree that in the rotating mass on a string example it is important to explain the continual inward acceleration and you can call the force on your finger holding the string the reaction to the inward force experience as an outward radial force, so we could refer to the radial forces of rotating motion to explain the tension in the string. The diagram is static and I believe it was D'Alembert who suggested in the 18th Century that to turn the rotation to a statics calculation you IMAGINE an outward force arithmetically correct as the centrifugal force. In modern terms you call up a rotating frame and explain the tension in the string as a fictional force arithmetically correctly in the same way. So it's just a name for the force on the constraint equivalent to the correct name for the force on the rotating mass. However it is an often used name so it deserves a place in the WP. Trying to see rotating systems as a statics problem like d'Alembert or by switching to rotating frames is, I suggest, confusing for the layman but the answer surely is not to ban the use of the word but to explain without maths the physical situation. I find the celestial examples difficult for different reasons, the nature of the gravitational pull is, what can I say, complex? , because while Newton and Einstein give us the maths to compute it, the physical explanation is still more difficult than a piece of string, however it is true that the gravitational effect of a planet on the sun is as real an effect as the centripetal effect of the sun on the planet. I am just asking for an explanation that explains why the mass rotates without saying that centrifugal force is fictional.Profstandwellback (talk) 14:54, 4 February 2011 (UTC)

If a tensile force exists in a restraining chain or cable it has to be the result of a force differential between two counteracting force entities. If one of the forces is the so called centrifugal force of separation of a rotating body from a spacially fixed axis of rotation, and is due to a phenomenon called the conservation of angular momentum, then the negating so called centripetal force is rather obviously due to an additional occurring circumstance which acts to prevent the occurrence of this angular momentum conservation property. Since this stasis of counteracting forces can be maintained without significant system kinetic energy loss over appreciable periods of time, we are evidently not dealing with a problem of dynamics, but rather with a problem related to the relationships existing between 2 different physical systems of motion.69.154.109.190 (talk) 17:38, 4 February 2011 (UTC)

Anon 69.154.109.190, The equal and opposite forces pulling at each end of the chain, such as to cause the tensile stress, would both be centrifugal forces. As regards angular momentum, it will certainly be conserved if there is no net torque acting on the system. But conservation of angular momentum is not a cause of centrifugal force as such. However, when angular momentum is conserved, the centrifugal force acting on a particle will obey the inverse cube law. As regards your point about there being two physical systems of motion, I can see both a radial and a transverse aspect to the analysis. Is that what you are talking about? David Tombe (talk) 18:20, 4 February 2011 (UTC)

Yes. And with regard to the force components causing the tensile stress in the cable, I cant see how either one can be more unreal than the other.WFPM (talk) 23:31, 4 February 2011 (UTC)

WFPM, Actually, it makes a good case scenario for explanatory purposes. We have two bodies in linear motion. They are connected by a loose string. At one instant, the string will suddenly become taut due to the centrifugal force exerted at each end. These two centrifugal forces form an equal and opposite action-reaction pair. The tensile stress caused by the centrifugal forces acting at each end of the string then causes an inward centripetal force to act at each end, and the two bodies will then move in mutual circular motion about the centre of mass. When the circular motion arises, the centripetal forces will be equal in magnitude to the centrifugal forces, so we will have two action-reaction pairs and four forces all of equal magnitude. Angular momentum will be constant because there will be no net transverse force acting on the system. If we nip the string in the middle and pull it shorter, the angular momentum (r^2.w) will be conserved, but the angular speed (w) will increase. Hence the centrifugal forces (rw^2) and the centripetal forces will be increased. David Tombe (talk) 01:07, 5 February 2011 (UTC)

(edit conflict) Profstandwellback wrote:

"In modern terms you call up a rotating frame and explain the tension in the string as a fictional force arithmetically correctly in the same way."

Is this really what you meant to write? If so, you are confusing two distinct concepts. I know of no competent physicist or mathematician who would call the tension in the string a "fictional force". The force exerted by the string on the rotating ball, the reaction to that force exerted by the ball on the string, the tension in the string, the force exerted by the other end of the string on the finger holding it, and the reaction to that force exerted by the finger on the string are all proper forces—their magnitudes remain the same no matter what coordinate system you use to describe them.

If you use a rotating coordinate system in which the coordinates of the ball remain constant, then those coordinates will fail to satisfy the mathematical expression of Newton's second law, because they are not changing despite the fact that the string is exerting a (proper) net force on the ball. If you wish, you can salvage Newton's second law in this coordinate system (at the expense of violating his third) by introducing a pseudoforce field whose outward force on the ball will exactly balance the inward force exerted by the string. But there are no reaction forces to those exerted by this field. The inward (proper) force exerted on the ball by the string, for instance, is not a reaction force to the centrifugal force exerted on the ball by this pseudoforce field. It is rather the reaction force to the (proper) force exerted by the ball on the string. The forces exerted by this pseudoforce field are the ones which physicists refer to as "fictional" "pseudo-", or "inertial", and they are completely separate entities to any proper forces acting in the system. Like Martin Hogbin, I don't see how blurring this distinction will enable a layman to understand what's going on.

David Wilson (talk · cont) 01:58, 5 February 2011 (UTC)

This happens all the time in physics where a simple single dynamic physical process is interrupted and/or otherwise modified by another physical process with a different criteria of operational performance. sometimes the different processes are reactionary as in this case, and sometimes they are more independent of each other, like in a spring-powered mousetrap. but the physical forces are real in any case.WFPM (talk) 03:11, 5 February 2011 (UTC)

Reactive centrifugal force references

I am removing references which, when you actually read them, do support the use the term 'centrifugal force' to refer to the reaction to the centripetal force, except erroneously or in casual speech.

Can we assume that you meant "do not support"? Not that I agree with it, but that must be what you're trying to claim here, yes? Dicklyon (talk) 21:04, 5 February 2011 (UTC)

Mook

This reference actually talks about their being what is sometimes called a centrifugal force and describes this force as a 'reactive, centrifugal' [note the comma] force. In other words, the source does not support the use of either 'centrifugal force' or 'reactive centrifugal force' in the context being discussed but merely points out that the force in question a reaction force and is centrifugally directed. The source supports only casual or informal use of the term 'centrifugal force' to refer to the reaction to the centripetal force. Martin Hogbin (talk) 10:02, 5 February 2011 (UTC)

Roche

This is clearly an essay against what the author sees as misuse of the term 'centrifugal force', although it is admitted that the term is still misused is some modern books the source is soundly against such usage in a technical context.

Here are two quotes to give this source's opinion on alternative meanings of 'centrifugal force':

Huygens’ mistaken version of the concept of centrifugal force continues in use outside physics to this day, despite efforts to banish it by very distinguished physicists...

For example, many students are likely to have absorbed uncritically the statement that the Earth’s attraction on the Moon is balanced by a centrifugal force. The standard physics response to this is to point out that if the force of gravity on the Moon were balanced, then according to Newton’s second law there would be no lunar acceleration, since there would be no resultant force, and the Moon would fly off at a tangent. Martin Hogbin (talk) 10:21, 5 February 2011 (UTC)

Bowser

This source is nearly a century old and cannot be used as a guide to modern terminology.

Holton

This source explains that centrifugal force is an illusion and never uses the term 'reactive centrifugal force' or the term 'centrifugal force' with that meaning. Martin Hogbin (talk) 17:40, 5 February 2011 (UTC)

Discussion

Martin, The quote from the reference which reads,

Huygens’ mistaken version of the concept of centrifugal force continues in use outside physics to this day, despite efforts to banish it by very distinguished physicists...

is very revealing. And there was you only a few days ago ridiculing the notion that there is any conspiracy involved in all of this. We clearly have a situation now in which 'very distinguished physicists' have been making efforts to banish the concept of centrifugal force. Is that what accounts for the remarks of David J Wilson above where he agrees that it is a real outward force which causes the tension in the string, yet claims that the so-called fictitious centrifugal force has got absolutely nothing whatsoever to do with causing this tension? Are we now living in an era where the writings of the great masters such as Huygens, Leibniz, Maxwell etc. can be overridden by the opinions of the people who have been writing textbooks in the last twenty years? And does this account for dicklyon's latest posting where he attempts to undo my claim that Goldstein didn't use a rotating frame of reference in his treatment of planetary orbital theory? I recommend that you carefully read dicklyon's latest posting because you will find that rather than undermining what I had said, that it actually confirms what I had said. David Tombe (talk) 12:54, 5 February 2011 (UTC)

Roche

@Martin - I disagree on the assessment of Roche. Note the other quotes from Roche:

"I have identified at least three interpretations of centrifugal force in the literature: a valid meaning in physics, an entirely different but equally valid meaning in engineering, and a cluster of false meanings."

and later, discussing the engineering definition

"But we must leave the final word to the engineers. The stresses that develop in rapidly rotating turbine blades are thought of by mechanical engineers as being due to centrifugal forces [20]. To take a simple example, an object whirled on an elastic string pulls the string outwards, creating the tension in the string. Both the inertial centrifugal force acting on the string and the elastic centripetal force acting on the moving body are reaction forces—they call each other into existence. Centrifugal and centripetal force are equal and opposite here but do not balance because they act on different bodies (figure 3).

In a rotating turbine, for example, each outer section of the blade exerts an outwards pull on the portion between it and the shaft, while at the same time the latter exerts an elastic inwards pull on the former. It is the stresses in the blades and their causes that mainly interest engineers, rather than the centripetal forces. It follows that both elastic centripetal forces and inertial centrifugal forces act in a rotating solid body [21]."

I think Roche is a bit confusing because he does not use the phrase "reactive centrifugal force" but instead uses "inertial centrifugal force" to describe this concept of centrifugal force that is used by engineers. But he is clear that these two uses are different, distinct, and in current use by a section of the modern scientific community. --FyzixFighter (talk) 15:15, 5 February 2011 (UTC)

I think Roche is so confusing about what he calls 'an entirely different but equally valid meaning in engineering' that this claim is no help at all. What exactly is this meaning? Martin Hogbin (talk) 17:28, 5 February 2011 (UTC)

From my reading of Roche, it's for describing the internal stresses within a rotating solid object, as described in the latter quote I mention. The stress on a given section of the body are the result that originates from the inward force from the adjacent section closer to the axis of rotation and the real outward force from the adjacent section just outside of the given section (which is a reaction-action pair with the inward force that the given section exerts on that adjacent section just outside). To me that seems pretty clear, but then again I've been doing a lot of reading lately on internal and external stress and strain. I wonder if perhaps ref. 20 (Mabie and Reinholtz) in Roche is clearer - anyone have access to it at the moment? --FyzixFighter (talk) 17:43, 5 February 2011 (UTC)

FyzixFighter, Roche says,

To take a simple example, an object whirled on an elastic string pulls the string outwards, creating the tension in the string. Both the inertial centrifugal force acting on the string and the elastic centripetal force acting on the moving body are reaction forces—they call each other into existence. Centrifugal and centripetal force are equal and opposite here but do not balance because they act on different bodies (figure 3).

and he is perfectly correct in using the term inertial centrifugal force. And he is correct when he says that the centripetal force and the centrifugal force are acting on different bodies, in that in relation to the centrifugal force he is referring to the knock-on effect which the inertial centrifugal force acting on the weight transmits to the string. The inertial centrifugal force causes the reaction with the string, and the centripetal force is a measure of that reaction, but it is only equal to the centrifugal force in magnitude in the special case of circular motion. The centrifugal force and the centripetal force are not an action-reaction pair. The action-reaction pairs in this case scenario are (1) the two inward centripetal forces acting at each end of the string, and (2) the two outward centrifugal forces acting at each end of the string. Roche also makes an intersting statement which I don't fully agree with,

It must be admitted, nevertheless, that this subject is subtle and the least confusing strategy for most physics groups may be to teach them centripetal force only, and leave centrifugal force to the engineers.

I think that if taught properly, physics students should have no trouble in grasping the concept of centrifugal force. Anyway, I'm glad that you decided to retain the Roche reference. As regards the Mook reference, I think that we're all agreed that it was confusing and that Martin was correct to remove it. David Tombe (talk) 16:07, 5 February 2011 (UTC)

I honestly can say I'm amazed. I don't think you and I read the same article. Your summary of Roche's comments bear hardly any resemblance to what Roche actually said and is so badly mangled that I don't know where to begin. Let me just be content to correct your glaring mistakes in summarizing Roche: Roche is very clear that there is no real, or proper as another editor has said, centrifugal force acting on the weight on the end of the string. The motion of the weight requires no outward force acting on the weight, only an inward force. Roche is very clear that the centripetal force from the string on the weight and the real "inertial centrifugal force" from the weight on the string (what we've been calling the reactive CF) are a action-reaction pair, and so are always equal in magnitude (even if the path isn't circular). I could go on about the physics but we've all been down that road before of trying to explain to you proper physics that I doubt the results of another attempt would be any different. To any reasonable editor who looks at the article and David's summary, I hope that it is painfully obvious just how much David invented and injected to twist Roche around to support his fringe ideas. --FyzixFighter (talk) 17:29, 5 February 2011 (UTC)

The text to which Roche is a reference is The concept of the reactive centrifugal force is used often in mechanical engineering sources that deal with internal stresses in rotating solid bodies. Can anyone show me where Roche says this. Martin Hogbin (talk) 18:47, 5 February 2011 (UTC)

Martin, Roche doesn't say this anywhere. Roche talks about 'inertial centrifugal force'. FyzixFighter put the reference in as evidence of the use of the term 'reactive centrifugal force', and now FyzixFighter is arguing that Roche was wrong in using the term 'inertial centrifugal force'. So the reference obviously doesn't back up what it was intended to back up. David Tombe (talk) 19:50, 5 February 2011 (UTC)

@Martin - How is that not an accurate summary of the engineer's concept of reactive centrifugal force that Roche describes on pg 403 (which I quoted above)? --FyzixFighter (talk) 20:04, 5 February 2011 (UTC)

Roche refers to the 'the inertial centrifugal force acting on the string'. There is no inertial (as in fictitious) force acting on the string just the reaction to the centripetal force applied by the string to the weight. That may be what Roche actually means but I do not think such a confusingly worded statement should be used as a reference. It is not even clear what reference frame Roche or the engineers he describes are using. Maybe the engineers are thinking in terms of a rotating reference frame, who knows? Martin Hogbin (talk) 21:20, 5 February 2011 (UTC)

Martin, Roche is correct in his usage of the term 'inertial centrifugal force'. You seem to think that the only centrifugal force involved is a reaction to the centripetal force. But what causes the centripetal force? The centripetal force is caused by the tension in the string. And what causes the tension in the string? It's caused by the inertial effect of the weight tugging on the end of the string. Ie. the centripetal force is caused by the inertial centrifugal force. It's just as Roche says. It's a shared reaction. David Tombe (talk) 21:29, 5 February 2011 (UTC)

@Martin - Here is where I find it necessary to carefully read Roche. It seems clear to me that he using the adjective "inertial" to signify that the engineering CF is an inertial reaction, ie a reaction force due to the weight's inertia, and not to signify that it is a "fictitious" force. That's why he explains that this engineering CF is exerted by the weight on the string (or by an outer section of the turbine on an inner section), and not (like what Roche calls the "fictional CF" of rotating frames) on the weight itself. In the caption for figure 3, Roche calls it the "centrifugal inertial reaction". What frame is irrelevant, since the force and the internal stress exists independent of frame. I do agree that Roche's use of "inertial" to describe the engineering is confusing and probably not the best choice given that the rotating frame force is also called an inertial force in other sources, but it is clear that Roche sees the two as separate and distinct concepts. --FyzixFighter (talk) 21:49, 5 February 2011 (UTC)

FyzixFighter, An action-reaction pair have to act on the same body. Roche points out that the centrifugal force and the centripetal force are not acting on the same body. You say that Roche makes it very clear that the centrifugal force and the centripetal force are an action-reaction pair. Show me where he makes this claim? David Tombe (talk) 20:29, 5 February 2011 (UTC)

In the usual concept of a reaction force, a force of object A pushing on object B is accompanied by a force of object B pushing back on object A. A planet and its sun, for example; or two adjacent elements of string under tension. I've never heard of this "have to act on the same body" idea before. Dicklyon (talk) 21:02, 5 February 2011 (UTC)

Dick, I don't know where I got that idea either. I've striked it out. But nevertheless, a centrifugal force and a centripetal force are not an action-reaction pair. They are two independent forces. They only happen to have the same magnitude in the special case of circular motion. David Tombe (talk) 21:19, 5 February 2011 (UTC)

In the fictitious-force definition, as in Goldstein's planetary orbit equation, they are completely independent and unequal (except equal in circular orbits where they r is constant because they are equal), I agree. But the "reactive" CF is the equal and opposite reaction force by definition; to say they are not an action–reaction pair is just to say that you're talking about something different; that's OK, just don't confuse what you're talking about with the reactive CF. Dicklyon (talk) 21:30, 5 February 2011 (UTC)

Dick, OK, that's a good start. You acknowledge that the inertial centrifugal force is not in general equal to the centripetal force. But you are talking about something different. I suggested that this 'different' quantity which some of you are referring to as 'reactive centrifugal force' is maybe a centrifugal force analogue to apparent weight, in which case it will always be equal to the reactive centripetal force, just as apparent weight is always equal to the normal reaction in gravity problems. I can indeed see an action-reaction pair here. But I have never seen any sources which totally divorce 'reactive centrifugal force' from inertial centrifugal force. Roche certainly doesn't do it. He knows that the inertial centrifugal force is the driving force behind the tension in the string. There will never be a so-called 'reactive centrifugal force' unless there is also an inertial centrifugal force involved. David Tombe (talk) 21:51, 5 February 2011 (UTC)

At least two of the four removed refs support the usage discussed

Martin, I don't think your reasons justify the removal of most of those references. The fourth I agree does not support the usage of centrifugal force as a reaction force, even though it does discuss that reaction force. The fact that Bowser is 90 years old doesn't really detract from its value, since it's correct and pretty much in agreement with current usage. Roche discusses the "centrifugal inertial reaction of the mass M on the string", which is the same thing as what we're calling "reactive centrifugal force", so it could be used to describe the concept better, but not the support the term per se. Mook's "a reactive, centrifugal force" is exactly what we're calling "reactive centrifugal force", that is, a reactive force that is centrigually directed. We should definitely keep that one. So I think I'll restore Bowser and Mook, and maybe Roche as an alternative way to describe the concept. Dicklyon (talk) 21:02, 5 February 2011 (UTC)

Bowser

You use a circular argument with Bowser. Bowser shows that reactive centrifugal force is a current concept and current usage shows Bowser is right.

I don't claim that Bowser shows that reactive cf is a current concept. But it clearly is, given the number of people still trying to make it go away. Dicklyon (talk) 21:48, 5 February 2011 (UTC)

So if Bowser does not show reactive cf is a current concept why is it given as a reference? Martin Hogbin (talk) 00:48, 6 February 2011 (UTC)

Good point; use this one instead; or this one; or this one; or this one; or this one; or this one. There are more. Also lots of sources that completely confuse the issue, talking about equal and opposite reaction forces and pseudo or fictitious forces all in the same breadth, not being clear about what force is on what. Those authors really need to know that there are two distinct conceptions called CF, namely the two compared in the table in this article. It would be fair to state that they are often conflated (we do say that, I think); many examples could be provided. Now I really do need to stop this. Dicklyon (talk) 01:21, 6 February 2011 (UTC)

Dick, I hope you are not thinking of leaving this page completely. At present it has fallen victim to the crazy physics of David Tombe and Brews Ohare. It desperately needs changing to a version which represents the understanding that most physicists, mathematicians, and engineers have had for the last half-century or so. You are perfectly correct when you say that lots of sources completely confuse the issue. It is only in the last several decades that the consensus has emerged not to use the term at all in inertial frames but to use it only to represent the fictitious/pseudo/inertial force invoked in rotating frames of reference. The rest is of historical interest only and should be treated as such by WP. Martin Hogbin (talk) 09:29, 6 February 2011 (UTC)

We can fix that without denying the other point of view. Sweeping it under the rug of history will just make it harder for people to understand the different things that they read in current books that still use the old way. Dicklyon (talk) 17:30, 6 February 2011 (UTC)

I am not proposing that we sweep anything under the rug or deny the existence of another POV. My preference would be to have one article on cf which deals principally with the inertial force but has a section section on 'alternative meanings' or the like on which we discuss older and alternative meanings of the term. I think it would be a good idea to explain in that section why thinking on the subject has changed and how some older usages caused confusion.

I would like to make the article of use to a wide range of readers but if some beginners form the opinion that cf is not particularly relevant to their current studies that would not be a bad thing. The real problem I see now is that the articles give the impression that there is serious current debate about what centrifugal force is, which I do not believe is the case. That problem in my opinion has been caused by a 'Google jockey' style of editing by some which has resulted in a bloated and unhelpful article which gives too much weight to fringe, specialist, and historical meanings. Martin Hogbin (talk) 19:50, 6 February 2011 (UTC)

Having looked at you examples I have to admit that there are indeed sources which describe 'centrifugal force' as the reaction to the centripetal force. I would ask you to note, however, that none of these sources actually uses the centrifugal force in any calculation or as a useful concept. It seems to me that the authors are worried that the student may have already heard the term 'centrifugal force' and that a 'harmless' definition of the term is required to try to prevent them from understanding the term in the confused way that many people seem to. I still remain convinced that the modern thinking is simply not to use the term at all at an elementary level and that this article should reflect that view. Martin Hogbin (talk) 09:41, 6 February 2011 (UTC)

I agree that it's not the best approach for most problems, but I did point out one book with an example problem worked with this approach. If you want the force on a roller-coaster track or something like that, it's the ideal approach. If you want to reflect the "modern thinking", then a short section backed up by a source that actually contrasts the points of view and argues for the modern one would be needed. Dicklyon (talk) 17:30, 6 February 2011 (UTC)

If you want the force on a roller coaster you need to calculate the reaction force from the car, that is fine but, there is no need to give this force a specific name, especially one that is better used for a different concept. I agree that this sometimes done and we should report that here but we should not give this obsolete and confusing usage equal weight to the inertial force. Martin Hogbin (talk) 18:06, 6 February 2011 (UTC)

Mook

The argument is about whether the term 'reactive centrifugal force' is in current common use. There is no doubt that there is a centrifugally directed reaction force to the centripetal force but Mook specifically avoids calling it the reactive centrifugal force'.

General

Dick are you claiming that engineers still use the term 'reactive centrifugal force' (or just 'centrifugal force' to describe the same concept)? No one has yet shown how this concept is helpful to engineers or anyone else. Martin Hogbin (talk) 21:30, 5 February 2011 (UTC)

I'm not claiming that it's a major usage, but the sources do suggest that it's still out there. Particularly Angelo. You can just say he's wrong, but it's wishful thinking to say that everyone has come around to seeing CF the way physicists and most engineers see it. Dicklyon (talk) 21:33, 5 February 2011 (UTC)

And I am not claiming that nobody at all ever uses the term that way but it is definitely a minority usage and the article should therefore describe it that way. Can anyone give a modern example where the concept of 'reactive centrifugal force' is actually used to solve a problem? Martin Hogbin (talk) 21:38, 5 February 2011 (UTC)

What you call it doesn't have a lot of impact on how you solve problems, like maximum speed of a vehicle on a curve before skidding. But here's one that does use "centrifugal force" and "centrifugal reaction" as the force equal and opposite to the centripetal friction force on the vehicle. Dicklyon (talk) 22:18, 5 February 2011 (UTC)

That is not an example of reactive centrifugal force. The reactive centrifugal force in that example would be the force exerted by the tyres on the road surface. This is clearly not relevant to the tipping of the vehicle and has nothing to do with D'Alembert's principle. The rather confused text does actually make some kind of sense in a reference frame rotating with the vehicle but nothing in the text actually tells you that this is the case and the centrifugal force is not even marked on the diagram.

The problem is a perfect example of the confusion that arises when the term 'centrifugal force' is misused. I would not want to insult engineers by suggesting that is how they like to think. Martin Hogbin (talk) 00:45, 6 February 2011 (UTC)

You're right; that's a confused bad example. I was looking for one where the reaction force of the tires on the road is compared to max frictional forces to see when the tires would skid. This isn't that. Dicklyon (talk) 20:30, 6 February 2011 (UTC)

Martin, I don't know whether or not the term 'reactive centrifugal force' is in widespread use. I certainly never heard the term until I saw it on wikipedia. But it would be a great help if more effort were to be made in trying to understand what those who use it are getting at. It would seem to me that the term is being used to describe the degree of reaction which an inertial centrifugal force induces on a string, spring, or a surface. And depending on the degree of centripetal reaction that it induces, it may not necessarily have the same magnitude as the inertial centrifugal force which is driving it. I see the major problem here as being that there are some who are willing to accept that inertia presses or pulls. They are willing to accept that there is an inertial centrifugal force as viewed from a rotating frame of reference. They are willing to accept that the pull or push of the inertia causes a reaction which they are willing to call 'reactive centrifugal force'. Yet, they are unwilling to join it all together and accept that the 'reactive centrifugal force' is being driven by the inertial centrifugal force. That is the whole problem in a nutshell. In fact, I would sum up by saying that having studied all of this carefully, that there are indeed two distinct concepts of centrifugal force, (1) Inertial, and (2) Reactive, but that they are so closely connected that it is ridiculous to split them into two different articles. (1) would be analogous to gravity, where (2) would be analogous to apparent weight. (1) would never form an action-reaction pair with centripetal force, whereas (2) does form an action-reaction pair with centripetal force. (1) is the centrifugal force of Leibniz, whereas (2) is the centrifugal force of Newton. David Tombe (talk) 22:07, 5 February 2011 (UTC)

Nothing but nonsense. Statements like "And depending on the degree of centripetal reaction that it induces, it may not necessarily have the same magnitude as the inertial centrifugal force which is driving it" and "They are willing to accept that the pull or push of the inertia causes a reaction which they are willing to call 'reactive centrifugal force'" simply convey a complete misunderstanding of the two self-consistent ways to look at centrifugal force. Your own "centrifugal force" is an unspecified vague concept without physics attached. The phrase "inertial centrifugal force" that you like to use can only have meaning within the context of a system of forces and accelerations and reference frames that make sense of it; we have two such, and you have no alternative. Dicklyon (talk) 22:23, 5 February 2011 (UTC)

Dick, the way in which you understand the two concepts is anything but self consistent. In your understanding, the inertial force can be present yet not in any way causing the reactive centrifugal force. That doesn't make any sense at all. David Tombe (talk) 22:29, 5 February 2011 (UTC)

You got that right: it doesn't make any sense at all. Please don't attribute it to me. Dicklyon (talk) 22:53, 5 February 2011 (UTC)

Your comments are rude and deliberately disruptive in trying to thwart progress in resolving this problem. I think you should be blocked from further editing on this topic.72.64.36.48 (talk) 22:59, 5 February 2011 (UTC)

You're right; I've let David creep me out again. I'll voluntarily withdraw from this nonsense and leave CF to others to fight out. Dicklyon (talk) 23:12, 5 February 2011 (UTC)

Dick, The literature is a complete monumental morass of confusion. I was trying to tie it all together in a rational manner. First of all there are editors here arguing about whether or not the concept of 'reactive centrifugal force' even exists or not. Then there are editors who believe it exists and that it is a completely distinct concept from the inertial centrifugal force. I have finally concluded that it is a distinct, but closely related concept, and that we can't have a 'reactive centrifugal force' without having an inertial centrifugal force to drive it. And all you can do is say 'nonsense'. You're not being very helpful. David Tombe (talk) 23:29, 5 February 2011 (UTC)

I think we are going in circles: I have taken the first few lines and reworked them to what I think is a better start:

Centrifugal force (from Latin centrum "center" and fugere "to flee") represents the effects of inertia that arise in connection with rotation and which are experienced by the constraint as an outward force away from the center of rotation. The mass which is rotating experiences the inward radial centripetal force because to deviate from a straight line it must accelerate towards the centre of rotation, in accordance with Newton's first and second laws. The term is also sometimes used in Lagrangian mechanics to describe certain terms in the generalized force that depend on the choice of generalized coordinates. The concept of centrifugal force is applied in rotating devices such as centrifugal pumps, centrifugal governors, centrifugal clutches, centrifuges, etc., as well as in centrifugal railways, planetary orbits, banked curves, etc. These devices and situations can be analyzed either in terms of the so called fictitious force in the rotating coordinate system of the motion relative to a center, or in terms of the centripetal and centrifugal forces seen from a non-rotating frame of reference. I cannot see the need for another article on the reactive centrifugal force, I cannot find that term in regular use and the "reactive" is unnecessary in the name although it can be discussed in the later analysis.Profstandwellback (talk) 17:34, 6 February 2011 (UTC)

I think that a clearer wording of what you mean would be:

'Centrifugal force (from Latin centrum "center" and fugere "to flee") is the outward force experienced by anything that constrains a mass to move in a circular path'.

The only problem with this is that it is not the meaning of 'centrifugal force' used by mathematicians, physicists, and I believe most engineers. It is a contrived usage used by some to justify continuing with obsolete, vague and confusing terminology.

Your proposed text goes on to read, 'The concept of centrifugal force is applied in rotating devices such as centrifugal pumps, centrifugal governors, centrifugal clutches, centrifuges'. The problem here is that the force described earlier is of no use at all in explaining how any of the above devices work. In fact in giving a clear explanation of how these devices work to laymen or beginners the term 'centrifugal force' is best not used at all (note that does not stop the word 'centrifugal' from being applied quite correctly to the devices themselves).

I do not object to stating that the term is used in the way you describe by some people but we cannot use the obsolete and unhelpful meaning as the principal subject of this article. Martin Hogbin (talk) 18:35, 6 February 2011 (UTC)

Martin, I agree that we don't want these changes that would make the reaction force the principal topic of this article. We already have Reactive centrifugal force for that. This article was built as a summary-style overview to help people understand the relationship between that one and Centrifugal force (rotating reference frame). I think we need to maintain it as such. Dicklyon (talk) 20:28, 6 February 2011 (UTC)

You seem to agree with me that Centrifugal force (rotating reference frame) is the mainstream current view of this topic but you still want to keep a summary style page that gives nearly equal weight to an outdated view of the subject. Why?

From the comments that have been received, I do not think this article helps explain anything, in fact it adds a lot of unnecessary confusion. Martin Hogbin (talk) 00:17, 8 February 2011 (UTC)

Martin I have no objection to your first sentence amendment. If you agree this is a true description of centrifugal force, is it not OK as a refutation of any false concept of centrifugal force? I am not sure what you mean by the meaning used by engineers etc where I accept there exists confusion, but not universally, most enginners and physicists seem to know the different ,inward vs outward, etc. there only remains the extension into the generalised case of instantaneous curved path other than the speciual but common case of circular rotationProfstandwellback (talk) 20:19, 6 February 2011 (UTC)

But your proposed sentence, and Martin's amended version, are only appropriate to the article Reactive centrifugal force, which I think we all agree is the minority or obsolete usage. The mainstream modern usage, the Centrifugal force (rotating reference frame), which Martin argues is pretty much the only one we should pay attention to, is excluded by the new lead sentence. Don't go there. Let this article compare and contrast the two conceptions, as it was created to do. Dicklyon (talk) 20:46, 6 February 2011 (UTC)

yes I am not interested in reactive centrifugal force, it's a tautology for me, as for "common" use I am not entering as a physicist, the advanced physicist knows all this stuff, but trying to start with a layman's enquiry as a teacher. The rotating frame of reference is of course valid but I maintain the layman enters from a fixed frame without knowing what that means and we should start from there and move on the the more complex maths and non circular cases. It seems to me there is agreement we need to dispel any false notions about the forces in rotation and this requires, I think, a very simple and clear starting point. The engineering bias of my comments is I think closer to the common man the the physics or maths approach just because of the many practical examples. We do not dispel a confusion by insisting on a rotating frame of reference which leaves the newcomer cold. There will always be a close relationship between centripetal and centrifugal, we could (as the article does) just concentrate on the inward/ outward definition of radial forces. My own feeling is to avoid calling (for the layman) any force a "fiction" because it is alienating. I maintain that to explain centrifugal applies to the constraint actually introduces the novel idea that to get rotation you have to constrain a mass. This is the crucial understanding step, so "centripetal" is more important actually but that does not remove the need to explain centrifugal from first principles.Profstandwellback (talk) 21:58, 6 February 2011 (UTC)

Prof, it is not clear to me exactly what your understanding of cf is. You say, 'Centrifugal force (from Latin centrum "center" and fugere "to flee") represents the effects of inertia that arise in connection with rotation and which are experienced by the constraint as an outward force away from the center of rotation'. The force you describe is the reaction to the centripetal force, what is called here the 'reactive centrifugal force'. You also say, 'I am not interested in reactive centrifugal force...', so what exactly are you referring to when you say centrifugal force? Martin Hogbin (talk) 23:10, 6 February 2011 (UTC)

Prof, I think we need to just tell it like it is, to avoid POV issues. I don't agree that "there is agreement we need to dispel any false notions...". We can simply ignore false notions and put what's true; that's what an encyclopedia does. What's true is that there are two distinctly different yet each individually correct and consistent conceptions of centrifugal force in mechanics (both can lead to correct analyses, even though they are not equal forces, and act on different bodies). You and Martin have argued to focus on the one and on the other. Each has its own article where you can do that. This article is to help people figure out which one they want. It is perhaps unfortunate that the term centrifugal force is used for both, but that's the reality that we have to live with. Dicklyon (talk) 23:18, 6 February 2011 (UTC)

Profstandwellback, I would support your proposed introduction. The so-called 'reactive centrifugal force' which they have been talking about would seem to be the interactive effect which arises in conjunction with strings, springs, and surfaces. Centrifugal force can of course still arise in the absence of any such interactive effects, such as in the radial gravitational field. I don't however support Martin's proposed amendment, because centrifugal force does not have to specifically arise in conjunction with a circular path. Angular speed about an origin is all that is required. David Tombe (talk) 18:57, 6 February 2011 (UTC)

David, if you accept this change, you're giving up on there being a centrifugal force on your planet. Is that better for you than admitting that the 1D (radial) system of Liebnitz and Goldstein is rotating? Seems like a bad idea. Dicklyon (talk) 21:01, 6 February 2011 (UTC)

Dick, There is only one centrifugal force. The Newtonian concept which you like to call the 'reactive centrifugal force' can only happen when it is being driven by an inertial centrifugal force. The introduction which Profstandwellback has suggested avoids going into the distinction between the Newtonian concept and the Leibnizian concept. Ideally that distinction should be treated in the main body of the article. Profstandwellback's introduction deals with centrifugal force in a manner which transcends the distinction between the two concepts. His wording correctly points out that centrifugal force (which of course is the centrifugal force in a planetary orbit) arises in connection with rotation. That part of the sentence caters for both Leibniz and also your favoured 'rotating frames' approach. Then he goes on to say that it is experienced by the constraint. That caters for the interactive aspect. Actually, on second thoughts, it might be better if that last phrase were to be re-worded as 'can be experienced by a constraint'. Anyway, one of the best sources of all for this topic is the one which you supplied last year, but which has now been removed. It is this one [5]. It clearly lays out the contrasting Newtonian and Leibnizian perspectives and it further gives the modern rotating frames perspective as supported by the author Dr. Swetz. This single source gives three perspectives on the topic, and a good coherent article could be written based on this source alone. David Tombe (talk) 22:52, 6 February 2011 (UTC)

The main advantage of the Centrifugal Force over a restraining Centripetal Force is that there are Engineering applications where the excess centrifugal force value can be used to do work (besides of course the centrifugal pump) such as in flotation applications, and in the rotating swing joyride, et cetera, where the centrifugal force value can be controlled to be mechanically useful. This leads to the concept that it should be considered to be the thing of primary consideration in these matters. A further discussion of this matter can lead us into a discussion of the whip principle, which is a different ball of worms about the same subject matter.WFPM (talk) 02:44, 7 February 2011 (UTC)

WFPM, That's exactly right. We are often looking at the excess of centrifugal force over centripetal force. David Tombe (talk) 14:21, 7 February 2011 (UTC)

Right. And that only make sense in the context of the fictitious force in a rotating frame. Dicklyon (talk) 19:06, 7 February 2011 (UTC)

Wrong. How could a fictitious force break through a centripetal constraint? You mean to say that if I spin up a system fast enough, and the stuff breaks out through the retaining wall due to centrifugal pressure, that we are dealing with a fictitious force? The fictitious force which you are talking about doesn't physically interact, according to some of the editors here. David Tombe (talk) 19:44, 7 February 2011 (UTC)

David, please read and try to understand a good modern text book on this subject. Martin Hogbin (talk) 00:19, 8 February 2011 (UTC)

Martin, You mean like the textbook that one of the editors further up the page got this out of,

The inward (proper) force exerted on the ball by the string, for instance, is not a reaction force to the centrifugal force exerted on the ball by this pseudoforce field. It is rather the reaction force to the (proper) force exerted by the ball on the string. The forces exerted by this pseudoforce field are the ones which physicists refer to as "fictional" "pseudo-", or "inertial", and they are completely separate entities to any proper forces acting in the system. Like Martin Hogbin, I don't see how blurring this distinction will enable a layman to understand what's going on.

This quote from higher up the page, says that the pseudo centrifugal force in the rotating coordinate system is a completely separate entity to any proper forces acting in the system. So according to this quote, the pseudo centrifugal force obviously can't be the centrifugal force which causes an object to break through the constraint in a rotating system when it exceeds the centripetal force. But dicklyon says above, in relation to such a situation, And that only make sense in the context of the fictitious force in a rotating frame. But on the contrary, it should be obvious that the force which causes the object to break through the constraint must be the one which you guys term the 'reactive centrifugal force'. And in this instant, it can't be equal in magnitude to the centripetal force, and so such a problem cannot be solved by considering only the centripetal force. We need to use what you call the 'reactive centrifugal force'. David Tombe (talk) 01:28, 8 February 2011 (UTC)

When you say "it can't be equal in magnitude to the centripetal force", the "it" can't be the thing that is defined to be the reaction force equal in magnitude to the centripetal force. It's not clear what your "break through" is about, or how it relates to circular motion, but I assure you the situation can be worked with proper forces and/or with pseudo forces if you know enough about the situation you're describing. Take your pick. Dicklyon (talk) 02:05, 8 February 2011 (UTC)

Stringing us along

Dick, It's quite simple. If you swing a weight on a string fast enough, the string will break. The centrifugal force has therefore exceeded the centripetal force. That's the "break through" that I'm talking about. And so I'm hardly going to take my pick from the two centrifugal forces which you have put on offer. The problem here is that the literature is a total morass of confusion which has enabled the writers of this article to falsely claim that there are two distinct centrifugal forces, one of which is real and one of which is not real. This in turn has enabled another editor to come along and try to sweep the real centrifugal force under the carpet on the false grounds that any problems involving actual physical interaction can be adequately catered for by the centripetal force. The truth is that there is only one fundamental inertial centrifugal force, as per Leibniz, and it can react physically with surfaces, strings, and springs, and it can work against gravity in a radial field. The thing which you call the 'reactive centrifugal force' is the knock on effect of the inertial centrifugal force when it physically interacts. David Tombe (talk) 10:10, 8 February 2011 (UTC)

The stone is swinging around and one lets go of the string. What happens? The stone continues its way in the tangential direction at that moment. It is obviously not driven by any kind of centrifugal force. At the time the string is released, the centripetal force from the holder through the string on the stone ceases to exist. And so does the reaction force (away from the holder) by the stone on the string. Simple? −Woodstone (talk) 13:06, 8 February 2011 (UTC)

Exactly. Martin Hogbin (talk) 19:22, 9 February 2011 (UTC)

Woodstone, We're not talking about letting go of the string. We are talking about the string breaking because of the centrifugal force exceeding the centripetal force. And in either case, the stone flies off both tangentially and radially. David Tombe 14:17, 8 February 2011 (UTC)

Never mind how the stone gets released, by detachment or breakage of the string, the stone will continue at constant speed tangential to the point where it was released. So there is clearly no force on it, and thus no centrifugal force. The point is that any perceived centrifugal force ceases to exist at the moment the centripetal force is removed. So it is justified to consider it a reaction force. −Woodstone (talk) 17:39, 8 February 2011 (UTC)

Better to consider, and call it, just a reaction to the certipetal force all the time (when working in an inertial frame) it needs no special name.

Woodstone, When released, the stone will move radially outwards from the origin in addition to the tangential motion which you mentioned, and there will be an inertial centrifugal force acting on it. The argument above is about whether or not that inertial force is interactive, and it obviously is, because it can push against a surface or pull on a string. David Tombe (talk) 18:47, 8 February 2011 (UTC)

Now you guys are getting into the whip principal, which is what happens when the restraining string is allowed to shorten by being wound up around the restraint. Then, in order to conserve the angular momentum (Mvr) value, the v has to increase as the r is reduced, and the centrifugal force increases as per v squared as the r approaches zero and the string will break and permit the release of the accumulated kinetic energy in the previously constrained mass. So the whip is a device that allows constrained kinetic energy of motion to be transferred away by making the force of separation greater than the constraining force of coherence.WFPM (talk) 16:18, 8 February 2011 (UTC)

David, the string breaks because the tension exceeds its strength. In the reaction force concept, centrifugal and centripetal forces are equal in magnitude by definition, being a reaction pair; they both go to zero when the break breaks and the string tension goes to zero. In the rotating reference frame concept, the CF doesn't change when the string breaks, but the centripetal goes to zero; the imbalance then accelerates the weight away from the center (in the rotating frame, that is, corresponding to a change from circular to straight-line motion in the rest frame). Your concept of centrifugal force exceeding centripetal applies in the rotating frame, since the centripetal went to zero, but not in the other; and it's not what breaks the string. It's when you mix these up and try to treat them as one CF that you get confused. Keeping the concepts separate makes the physics work, in the frame of your choice. Dicklyon (talk) 23:14, 8 February 2011 (UTC)

Dick, if as Woodstone says, the centrifugal force is only a reaction to the centripetal force, and that the centripetal force is the prime mover, then how come the centrifugal force exceeds the centripetal force and breaks the string? How can the reaction be greater than the action? And how can you say that the centrifugal force in the rotating frame is what exceeds the centripetal force, but that it's not what breaks the string? It is you who is totally confused. David Tombe (talk) 00:14, 9 February 2011 (UTC)

If you could read, you'd read my previous answers, and then read your question, and then regret that you wrote it. So learn to read, and leave us alone. Dicklyon (talk) 05:42, 9 February 2011 (UTC)

I re-enter this discussion in trepidation. The argument swings around. There are surely many frames of reference, two of interest, the static or to the layman, normal frame and a rotating frame centred on the (instantaneous) centre of rotation. However there is only one force diagram, looking at the string, there is the tension in the string caused by equal and opposite forces, one of which is inertial in origin, is a real force and has been called centrifugal force for a long time. The other is the force on the rotating mass which is centripetal. When we use a rotating frame all points in the frame are accelerating toward the centre so we have to remember that when analysing an apparently static situation. The real forces in the string must obviously stay the same whatever frame we use. So I would say there is only one force but there are different ways to look at that force. It is not true to say at the outset that there are two forces (depending on your frame of ref.) there is just one real force . However we all accept that the common confusion must be addressed in that the rotating mass is actually accelerating inwardly and the force on it is therefore clearly an inward force. I think the word constraint is useful in this context and is the word used in many textbooks, the mass is constrained to rotate. And repeating myself again, I maintain that the layman needs a direct explanation before introducing the maths and the rotating frames of reference which are routine for the mathematician but foreign to many who may turn to this page for an explanation. The use of the word fictional is rigorous in a rotating frame of reference to be sure, but that does not mean there are two centrifugal forces as stated in the first few lines at present.Profstandwellback (talk) 17:27, 9 February 2011 (UTC)81.155.109.9 (talk) 17:26, 9 February 2011 (UTC)

This is nonsense: "It is not true to say at the outset that there are two forces (depending on your frame of ref.)" In fact, as the article says and compares, the two CFs act on different bodies, have different values, and one is a pseudo force due to the frame. How can you then attempt to treat these as one? The only way forward is to admit their difference, and deal with them independently. Of course, the tension in the string won't depend on which analysis approach and CF definition you choose, but you have to do it right. Don't think "there are two CFs", but rather "there are two things called CF". Dicklyon (talk) 18:31, 9 February 2011 (UTC)

Prof, this is not really a subject for speculation, it is well understood. In a frame rotating with the string there is an inertial (also known as a pseudo or fictitious) force which is called centrifugal force. It acts on the stone in an outward direction and is equal and opposite to the centripetal force, which also acts on the stone but in an inwards direction, thus the net force on the stone is zero and, as a consequence, the stone remains stationary in the rotating frame.

In an inertial (non-rotating) frame the centrifugal force described above does not exist and is not required. The net force on the stone is not zero, it is the centripetal force being applied by the string, thus the stone accelerates in the direction of the net force, which is towards the centre, causing it to move in a circle rather than in a straight line.

In the mind of all the world's mathematicians, physicists, and engineers the above is the only correct description of the forces acting on the stone. In both frames there is a tension in the string, caused by the reaction to the centripetal force applied by the string to the stone.

Unfortunately some people seem to complicate this simple explanation by using the word 'centrifugal force' to mean something else as well as the meaning described above. I cannot deny that some people do this but it causes endless confusion and the practice is best avoided by those who wish to understand the subject. Martin Hogbin (talk) 19:10, 9 February 2011 (UTC)

Dick, this is yet another demonstration of how confused people get when we use one name for two different things. I cannot deny that some people have done this but it is no way to write an encyclopedia. Martin Hogbin (talk)

So what shall we do? Deny the existance of one? Or the other? Dicklyon (talk) 02:31, 10 February 2011 (UTC)

No, of course not but we should structure the article to distinguish between the approach which is currently used and recommended by almost everyone and an outdated use of the term which has caused confusion in the past and still is now. Martin Hogbin (talk) 09:38, 10 February 2011 (UTC)

OK I am going to give up with this final comment. Rotating frames of reference are tricky; early observers assumed an Earth centred system and while the sun and moon behaved themselves the planets accelerated, decelerated, stood still and went backwards requiring complex imaginary forces and mechanisms (constraints) to explain their movement. The picture is much clearer in a static frame if you can find one. We must be humble because explaining gravity, mass and inertia remain the greatest challenges in physics today. How would you know if you are in a rotating frame? You look for centrifugal force clues.Profstandwellback (talk) 09:07, 10 February 2011 (UTC)

Yes, I agree, rotating frames are tricky and are best not used by beginners, who are best to stick to Newton's laws in inertial frames. If you do this, there is no need to invoke the concept of centrifugal force at all. Everything can be explained without using it. Martin Hogbin (talk) 09:38, 10 February 2011 (UTC)

OK, but what changes to the article do you recommend based on these positions? Dicklyon (talk) 15:33, 10 February 2011 (UTC)

My suggestion is, as before, that we have one article on cf, concentrating principally on giving a clear description of the inertial (rotating frame) force, aimed at the widest range or readership possible, starting with the simplest and clearest non-technical description that we can muster and proceeding to a more mathematical analysis.

We should also include a section on older and specialist meanings of the term. Perhaps the article should start with a note that there are several meanings to the term but only one regularly used and especially taught today.

Or maybe, as you prefer, we should keep this article as the introduction to the subject with links to the more detailed discussions in individual articles, but structure it as I have described. At the moment it gives far to much weight to outdated and specialist definitions. These should just be briefly mentioned here and then linked to the individual articles. Martin Hogbin (talk) 16:54, 10 February 2011 (UTC)

But Martin, I don't see how that squares with the general agreement that "rotating frames are tricky and are best not used by beginners." Focusing on rotating frames of references will deny the ordinary layman of hearing a satisfying explanation why he feels an outward force when he swings a weight around on a string, or will deny him the satisfaction of being able to connect the concept of "centrifugal force" to that, as so many books still do (especially outside the technical physics/engineering community, but even some within it). Dicklyon (talk) 21:00, 10 February 2011 (UTC)

That is a good point but one, I believe, that we must face up to. I see no point in giving some apparently satisfying explanation that is actually quite unhelpful. I see still less point in giving several meanings and expecting the reader to take their pick. There are many people who use the term without having much idea exactly what it is, hoepfully this articla can explain it to them. There may be other readers without much idea what cf is. Better to tell them that cf is rather complicated and if they are not going to try to understand the subject properly they are much better off ignoring the term cf and getting on with physics in inertial frames without it. This is how physics is taught today. Martin Hogbin (talk) 00:12, 11 February 2011 (UTC)

You might start out by explaining how a centripetal force is capable of controlling the details of centrifugal motion activity without ever acting through a distance and thus doing any work, whereas the centrifugal force is capable of being used to do work.WFPM (talk) 18:01, 10 February 2011 (UTC)

I have no idea what this comment is trying to refer to or what position you are trying to advance. Maybe an example source would help. Dicklyon (talk) 21:00, 10 February 2011 (UTC)

If the inward acceleration in circulatory motion is controlled by a "centripetal force", then the result of the application of the force should result in not only an acceleration but a displacement of the material in the direction of the force. However, since the centripetal force does not act through a distance to do work on the matter of the system, it would appear that the matter has, in some manner, achieved a circularity of motion that does not involve a force times distance activity created by the matter of the container, but this is a violation of Newton's first law. A logical argument would be that the instantaneously translating portions of matter would be trying to linearly continue to translate and thus impact against the material of the container where they would first exert a force which would then be counteracted by the reactive repulsive force of the container materials. This allows a consideration of the slowing down activities of the matter due to the interaction of the centrifugal force values with the forces in the wall of the container.WFPM (talk) 22:03, 10 February 2011 (UTC)

I don't think I'm going to be able to deconfuse you, or to follow you. It would be best to stick to using this talk page to discuss how CF in reliable sources is represented in our articles. If you have sources that present CF in a way that you think is correct and less confusing, please do bring those up. If you have suggestions for what to change in the article to make it more clear, we'd love to hear them. But if you're just here to try to solve your own confusion about CF, this is not a good use of the talk page. Dicklyon (talk) 22:17, 10 February 2011 (UTC)

Well since you're creating a compendium of information about the subject matter, I guess you're doing what you should do under the circumstances. But the idea that the talk sect is not about the subject matter confuses me more and biases everything in favor of the status quo of knowledge. And I would like to know how a circulatory system gets rid of excess energy and/or angular momentum, and I think that the Centrifugal force entity is the subject matter for that and I thank you for your attention.WFPM (talk) 22:58, 10 February 2011 (UTC)

Starting over

Now that David Tombe is again banned from commenting on physics topics, I suggest we start over and have a more focused discussion on how best to represent the two distinctly different conceptions of CF that this article introduces, and that we have separate detailed articles on.

My own proposal is to leave this article pretty much as it is, and to work on un-bloating the others. Other opinions should be stated here now, so we don't have to try to infer them from the mess above. Dicklyon (talk) 21:11, 10 February 2011 (UTC)

I would rather start on this article making it concentrate on the modern meaning if the term but linking to the other articles, which I agree do need some editing. Martin Hogbin (talk) 00:14, 11 February 2011 (UTC)

I wouldn't object to seeing something on modern suggestions for how the term should be used. I know we had looked at various sources that advocated only using the modern interpretation, so something on that would be good. But too much "concentrate on" I might push back on. Dicklyon (talk) 00:27, 11 February 2011 (UTC)

Well, just between us Engineers, How does a Centrifugal pump transfer kinetic energy into the material that's being handled?WFPM (talk) 00:58, 11 February 2011 (UTC)

Yeah, that article's not very clear. Why don't you research it and let us know? Dicklyon (talk) 01:14, 11 February 2011 (UTC)

WFPM, there is no need to invoke a centrifugal force to explain how a Centrifugal pump works. It is not much different from a bat hitting a ball, the bat moves in an arc but the ball continues in a straight line, just as in the pump the impeller blades move in a circle but the water continues in a straight line, which takes it towards the outside of the pump.

There is no advantage in just making up a force to explain something you do not understand. Martin Hogbin (talk) 09:22, 11 February 2011 (UTC)

Well the Centrifugal pump people passed it on to you guys and you don't like my logic I cant pass on OR. So I'd say that the system of information communication is pretty FUBAR amongst us volunteers. Maybe they know and are not telling you. I'd like to know. My 1947 Robeson Physics just says what you say. We evidently haven't progressed much in public knowledge about basic research. So Sad!!!WFPM (talk) 13:44, 11 February 2011 (UTC) Incidently, Your bat and ball analogy is interesting in that it involves the same unknown principles that we dont want to know about or discuss. However I dont consider it to be an engineering problem.WFPM (talk) 14:00, 11 February 2011 (UTC)

It is your goal to fill David's shoes here, or to help improve encyclopedia articles based on WP:reliable sources? Please consider the latter. Dicklyon (talk) 16:43, 11 February 2011 (UTC)

No. I like David, but I guess that I don't have a sufficient grasp of Mathematics to be able to deduce what I want to know from your explanation details. And understandable explanations is all that I'm after.WFPM (talk) 23:55, 11 February 2011 (UTC)

So what parts of the current article do you find hard to understand? That would be useful info here. Dicklyon (talk) 01:14, 12 February 2011 (UTC)

Well a first glimpse summary of the situation is to note that we're dealing with the activity of a quantity of matter that is in circular motion about an axis of rotation that is controlled by 2 opposing forces, and we note that energy is being carried away from the remaining matter as the result of the activity. This leads to the logical conclusion that the force with a directional component in favor of the resultant direction of activity is the one that is active in providing the work (force times distance) needed for this accomplishment. It also casts doubt on the validity of the concept of the existence of a working force in the direction opposite to the direction of the activity. We note also that any instant in time there is only translational motion, which is unidirectional, in accordance with Newtons first law, and which will continue, unless disturbed by a force, and thus lead to the conclusion that the operational force in this activity is that tending in the direction away from the axis of rotation. Of course the start of the discussion might involve a notation that a material system in rotation stores its kinetic energy in units of "angular momentum (Mvr), which takes into account the internal variation of the "kinetic energy (Mv^2)" value within the material system being managed. Need I go on?WFPM (talk) 17:54, 12 February 2011 (UTC)

I have no idea what you're referring to in saying "the activity of a quantity of matter that is in circular motion about an axis of rotation that is controlled by 2 opposing forces;" what two opposing forces? And "energy is being carried away from the remaining matter as the result of the activity" refers to what? The centrifugal pump? Your "logical conclusion" is uninterpretable without clarity of the assumptions that you deduced it from. If you want to understand the centrifugal pump, first understand the basics of centrifugal force; then decide whether you want to do your mechanics analysis in the stationary frame, or in the frame of the rotating water and impeller; then do it using known methods of mechanics. Your nonsense like "lead to the conclusion that the operational force in this activity is that tending in the direction away from the axis of rotation" is just crazy, since the deviation from straight motion is toward the center, making the motion curve toward circular; there is no motion with acceleration toward the outside of circular motion. No, you need not go on. Dicklyon (talk) 18:24, 12 February 2011 (UTC)

Like Dick, I have some difficulty understanding the point that you are making but, the first thing I would say is that, if you do not like the idea of working in a rotating frame with the associated mathematics, then do not do it. To analyse most rotating systems it is best to work in an inertial frame (which you probably do naturally without thinking about it) and just use Newton's laws and the real forces involved. As far as centrifugal force is concerned, forget about it, it does not exist in an inertial frame and there is no need to invoke it to explain anything.

[There is a conceptual difficulty here regarding the modern approach to cf in that this makes this into a kind of kamikaze article, since the first and most important point it needs to make is that in most circumstances the concept of centrifugal force is neither desirable nor necessary.]

Are there any examples where you think the concept of cf is necessary for an understanding of how something works? Martin Hogbin (talk) 18:36, 12 February 2011 (UTC)

I would propose debloating and fixing up Centrifugal force (rotating reference frame), merging in any unique information from this page that isn't found elsewhere, and renaming that to be simply Centrifugal force. The rotating reference frame centrifugal force is by far the most common usage (I think we all agree on that), even the usage of the layman (even though they probably don't realize it), and therefore the primary topic. According to WP:TWODABS:

"If there are only two topics to which a given title might refer, and one is the primary topic, then a disambiguation page is not needed – it is sufficient to use a hatnote on the primary topic article, pointing to the other article."

I think it's a whole lot easier to talk about the distinction between the two uses, the common physics usage and the other usage that appears to be mainly in use by mechanical engineering, and to clear up confusion between the two after clearly explaining the one or the other. --FyzixFighter (talk) 20:53, 11 February 2011 (UTC)

I think it's a misperception that MEs use the "other". They use the same fictitious force methods as physicists do, at least for any serious robotics work. But the "reaction force" idea is still around at a low level in both fields as well. I'd like to see a more complete proposal on how to proceed, as I remain worried that we're going to go too far over on endorsing one view and burying the other. I'm not so optimistic that we can succeed to "clear up confusion" in any case. Dicklyon (talk) 23:14, 11 February 2011 (UTC)

Your worry about endorsing one view over another is, in my opinion, caused by the Google and the internet. Using Google, it is easy enough to find published material supporting almost any opinion but not so easy to give different views the correct weights to represent current thinking on a subject. I believe that the article currently gives undue weight to obsolescent and unhelpful views on cf.

I also think that there is too much emphasis on the 'no OR' principle of WP. I agree with and fully accept the principle but think it is being pushed too far by some. Potentially contentious material needs a reference, especially if challenged, but not every statement needs one and, as editors, we are permitted to devise our own explanations rather than being required to plagiarise material from others for every word of the article. What we should not do is make up out own physics. I believe there is too much emphasis on a 'Google jockey' and cut-and-paste attitude to editing rather than editing based on a good understanding of the subject, supported by reliable sources. Martin Hogbin (talk) 10:32, 12 February 2011 (UTC)

I'm not following your complaint. Not sure who it is about, or what actions, or what material. If it's me, say so. Dicklyon (talk) 23:33, 12 February 2011 (UTC)

I was not referring to you or anyone in particular but I was trying to address your concern about endorsing one view and burying the other. My point is that, as editors we are entitled to some degree to decide on the most appropriate way of presenting a topic and, in this case, what definition of centrifugal force we should give more space and weight to.

We have two usages of the term cf but not two schools of thought each claiming the other is wrong. Many people think that the term cf should only be used in rotating frames and not used at all in inertial frames but I do not think that there is any significant school of though saying that the reactive concept is more useful, it may me used by some people, but I have not seen anyone who claims that it is a more useful concept. So we as editors are not bound to adopt a NPOV as we would, for example with a theist/atheist position, because there are not actually to POVs Do you see what I mean? Martin Hogbin (talk) 00:11, 13 February 2011 (UTC)

Centrifugal pump

Yes, because in the centrifugal pump we know that the energy entering the system is supplied by the impeller, which causes the material to move faster in a linear direction. Then something causes the material to deviate into a motion perpendicular to the axis of rotation, and in that direction indicated for the line of action indicated for the centrifugal force. So what causes that, if it isn't a real force?WFPM (talk) 22:31, 12 February 2011 (UTC)

You can see how the centrifugal pump works at the dinner table. Take a knife and hold it at one end keeping it flat to the table. Put the salt pot touching the knife at the same end as your hand then rotate the knife so that it pushes the pot round in a circle. As you push the pot round its inertia (and the friction with the table in this case) causes it to continue in a straight line rather than move round in a circle with the knife, thus the pot moves outward.

It just the same with the pump, the impeller blades move in a circle because they are fixed to the centre bearing but the water tends to move in a straight line thus water at the centre soon finds itself on the outside of the pump. No mysterious forces are needed, just Newton's first law that bodies continue in straight line motion. Martin Hogbin (talk) 23:18, 12 February 2011 (UTC)

Upon reflexion I can see that the reactive force from the circular container wall will provide a force that will deviate any stray motion of the increased velocity material (including the increased initial linear motion) back into into the flow channel in a direction consistent with continued circular motion, and thus could be considered as a reactive centripetal force, and neglecting frictional considerations, would not change the kinetic energy content of the rotating materials. Then, like you say, if the managed path is directed to be a closed circular loop, then I guess that you wouldn't need a concept of a centrifugal force to accomplish such an activity. Have you tried out this idea on your Centrifugal pump people?WFPM (talk) 00:59, 13 February 2011 (UTC) Boy!!! That was a quick solution to the Centrifugal pump article problem. Now what about the artificial gravity problem? Which concept of Centrifugal force is that?WFPM (talk) 01:53, 13 February 2011 (UTC)

Excellent, I am glad you liked my explanation. I also hope that you agree that referring to any particular reactive force as 'centrifugal force' is not necessary to understand the problem. The reactive force felt by the pump casing is just like any other reactive force, such as the backward force felt by the impeller blades. There is no benefit in giving it a special name. Martin Hogbin (talk) 11:43, 13 February 2011 (UTC)

I don't think removing "centrifugal force" from the explanation clarifies anything, and it takes it further away from all of the explanations that you'll find in sources. And the remaining "if the outlet of the pipe is too high or too restrictive to allow flow, the fluid kinetic energy imparted by the pump is converted entirely into static pressure" doesn't make a lot of sense, since it doesn't take any energy to make static pressure. I'll work on it... Dicklyon (talk) 17:39, 13 February 2011 (UTC)

Most situations are easiest to analyse in and inertial frame but some (weather systems on the rotating Earth, for example) are easier in a rotating frame.

It is interesting to look at the space station from both types of frame. As you cruise toward the station in your the inertial frame of your spacecraft you will see a large 2001-style wheel rotating. The people, with their feet in the outside rim are just like the water in the cf pump. Their natural inertia tries to make them continue in a straight line but the rim of the station continuously pulls them (applies a centripetal force to them) out of straight line motion. Thus there is a force between the people and the rim. Note that there is no force acting on the people pulling them in an outward direction only a force pulling them inwards.

But if I saw somebody next to the outside of the rim I would note that he is tethered to the outside of the rim, because if not he would drift away from the rim because of his slightly greater angular velocity.WFPM (talk) 21:15, 16 February 2011 (UTC)

WFPM, this is an interesting discussion but not strictly relevant to improving this article. We can continue on my talk page if you wish. Martin Hogbin (talk) 22:55, 16 February 2011 (UTC)

Well Okay, I'll leave the subject matter with you guys. Sorry we didn't get anything figured out.WFPM (talk) 00:35, 17 February 2011 (UTC)

I would be very happy to continue, just not here. Martin Hogbin (talk) 22:10, 17 February 2011 (UTC)

Now imagine someone standing in the space station. They may not consider the station to be rotating and may take the station itself as their reference frame. This presents the physicist and engineers on board with a problem. In their new frame of reference they are stationary, there is no gravity, yet things fall down towards the rim. Newton's law's, which tell them that things that are stationary remain stationary unless a force acts on them, fail.

Now wait a minute! If I'm inside the space station with no gravity, then the things that I have will likewise have no gravity and will not fall towards the space station rim. In order for that to happen, I would have to find something loose next to and moving alongside the rim that I could lift away from the rim and then let fall.WFPM (talk) 20:58, 16 February 2011 (UTC) So if I had a ball with no gravity and then lifted a ball away from the rim that did have gravity, the question would become as to what's the difference.22:46, 16 February 2011 (UTC)

If you'd indent your comments in from what you're responding to, and put them after what you're responding to, or ideally at the end even, it would be easier to follow; the paragraph below that looks like a reply to this was actually here earlier 3 days earlier. So I'll reply. Forget gravity; there's not any here. Inside the rotating station, in its frame, there is a pseudo force that people inside think of sort of like gravity; things on the floor will stay on the floor because of it. If you have something that's stationary in an outside inertial frame, like might be what's distracting you here, then those things are moving in the rotating frame, so there's also a Coriolis force, so it gets harder to describe. But I have no idea if that's what's in your mind when you say "the things that I have will likewise have no gravity and will not fall towards the space station rim." They WILL fall toward the rim if they start out unmoving in the space station. And gravity is just a pseudo-force, too, in general relativity, which just says that it comes from an accelerating reference frame, so this is not so different. "Fictitious" doesn't mean it's not real, just means it's due to the reference frame. Dicklyon (talk) 03:15, 17 February 2011 (UTC)

Agreed, that is an important point which some may not understand. ~~

I've been watching NASA and I don't think that anything that the floating scientists are carrying would "fall" in any particular direction since they stay with him unless he pushes them away. But in a rotating station a similar ball stationed against the rotating wall would resist being moved away from the wall. So let's let the 2 balls be identical and ask why the one against the wall requires an effort by the floating person in order for him to collect it from the wall. And the answer is that the ball against the wall has an amount of stored kinetic energy and angular momentum of circular motion around the rotation axis of the space station, and when he collects it he also collects the major part of that. and that after that time the second ball will stay with him but he will be slightly attracted towards the wall of the space station. So artificial gravity is an additional existence of differential angular momentum that you add to the components of a space station. I guess I'm not making much of a point here. But since we're dealing with the subject of centrifugal force, do you think that it is a factor in causing the spherical oblateness of the planet earth?.WFPM (talk) 17:10, 17 February 2011 (UTC)

Right. NASA doesn't have a rotating wheel-type space station. It's just inertial, so everything is weightless and CF-less. As for the rest, yes, you can explain forces in terms of changes of energy if you like, but you have to do it right, and it can't give different answers; I don't know what "collect" means in terms of forces and energy, but I'll assume you mean he moves it away from the wall toward the axis, in opposition to the outward pseudoforce, so it takes energy; in the inertial system the ball's angular momentum goes down, and it transfers energy to the rotation of the space station, which speeds up a bit. And yes "it" causes the spherical oblateness of the earth, depending perhaps on what you mean by "it". Dicklyon (talk) 17:21, 17 February 2011 (UTC)

The smart ones on board work out that the problem is due to the fact that their reference frame is non-inertial, it is rotating, Newtons law's only apply in inertial frames, in a rotating frame they need to be changed. As the people on board are rather fond of Newton's laws and would like to keep them unchanged, they solve the problem by inventing a force which pulls all masses outwards, this is the fictitious (they have just made it up) centrifugal force. Martin Hogbin (talk) 12:32, 13 February 2011 (UTC)

While I'm thinking please see article about operation of String trimmer.WFPM (talk) 18:02, 13 February 2011 (UTC)

You mean 'A string trimmer works on the principle that a line that is turned fast enough is held out from its housing (the rotating reel) very stiffly by the string tension that exerts the centripetal force that prevents the string from flying off in a straight line under its own inertia'. That is a very good description of what happens in the non-rotating frame of the user. Notice that centrifugal force is not mentioned at all. Martin Hogbin (talk) 22:58, 16 February 2011 (UTC)

But it was, until it was changed to Centripetal force. And I don't see how centripetal force can generate tension in a string.WFPM (talk) 00:50, 17 February 2011 (UTC)

I changed it to use the concept of centripetal force, because that's the force of the hub pulling on the string. It's what makes the string go around, and acts against the string's inertia to keep it under tension. Each mass element of the string has a net inward force making it go in a curved path, and those add up along the string to make an increasing tension near the middle, and minimal tension at the outside. The string also exerts a reactive centrifugal force on the hub, but that's less interesting. Dicklyon (talk) 03:05, 17 February 2011 (UTC)

But the string starts out at the loose tip with zero tension, and then with an incremental increase in each element of the length, which you say is a reaction to the strings inertia. But at any instant in time the inertia of the string is in its direction of motion, which is at right angles to the direction of the string's restraining force. So it looks like there is no force buildup and required increasing centripetal force in the string such as to cause an increase in the tension in the string.WFPM (talk) 17:40, 17 February 2011 (UTC)

When you, quite simply, analyse uniform circular motion you see that it consists of constant acceleration towards the centre. Tension in the string is caused when yo accelerate the tip towards the centre, just like you get tension in a tow rope when you tow a car from a standing start.

Can't see the analogy, because a tow rope doesn't have varying stress with distance in circular motion. And if I tried to rotate a string with any amount of length it would lose its ability to damage anything.WFPM (talk) 22:30, 17 February 2011 (UTC)

Flattening of Earth

See reference to Centrifugal force in article Flattening.WFPM (talk) 18:01, 18 February 2011 (UTC)

That would be in the rotating frame of the Earth. Martin Hogbin (talk) 18:26, 18 February 2011 (UTC)

You're confusing me about frames. I merely note that the earth rotates and the earth gets flat in the plane of rotation. This would imply the existence of a flattening force of matter repulsion in that plane whose direction must be away from the center of rotation. It is of course overpowered by the force of gravitational attraction, towards the center, but the situation stabilizes with with an increased diameter or oblateness of the sphere in the rotating plane diameter.WFPM (talk) 21:06, 18 February 2011 (UTC)

As I said before this is not really a matter for here, why not continue on my talk page? Martin Hogbin (talk) 21:22, 18 February 2011 (UTC)

Huygens origination of concept

In a book "Introduction to Newton's Principia", by I. Bernard Cohen, Harvard University Press, 1978, in a page 53 footnote, it says: In a manuscript written at about the time of E2 printed in supplement !, Newton said, in part, M'Hygens gave the name of vis centrifuga to the force by which revolving bodies recede from the center of their motion. Mr Newton in honor of that author retained the name and called the contrary force vis centripeta.WFPM (talk) 16:33, 26 February 2011 (UTC) Note that in the Huygens biography, he is credited in writing in 1673 about the "centrifugal force".

Your point? Huygens' coining of the term is mentioned in History of centrifugal and centripetal forces. --FyzixFighter (talk) 15:02, 27 February 2011 (UTC)

Well at the time Huygens was doing this activity, he was involved in the study of the Pendulum operated time measuring device, which he wrote about in 1673. However he must have then noted the time intervals of rotation of a pendulum and then paid attention to that. And that would lead him to the concept of an axial force away from the center of rotation, which he named vis centrifuga, and not necessarily in the existence of a centripetal force. Whereas Newton was studying the force keeping the planets in orbit and needed a centralizing force, which he called vis centripeta, with due credit to Huygens. It is an interesting sample of application engineering whereby you adapt whatever ideas you can find to your particular idea or application.WFPM (talk) 18:19, 27 February 2011 (UTC)

Requested move

The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was not moved.--Fuhghettaboutit (talk) 22:46, 31 March 2011 (UTC)

---

Centrifugal force → Centrifugal affect — The Centrifugal affect is not a force as it is commonly called but it is in fact an affect/reaction of the Centripetal force--BravoNovemberGolf (talk) 12:37, 25 March 2011 (UTC)

strong oppose . I think you mean 'effect' not 'affect', but in either case the common name by which it is overwhelmingly known is 'centrifugal force'. Yes it's a fictional force but that is explained in the article.--JohnBlackburne^words_deeds 13:06, 25 March 2011 (UTC)

Strongly oppose for the same reason that John Blackburne gives.

David Wilson (talk · cont) 13:19, 25 March 2011 (UTC)

Strongly oppose: John Blackburne couldn't have said it any better above. –CWenger (talk) 13:42, 25 March 2011 (UTC)

• Strong oppose, per John Blackburne. Andy Dingley (talk) 14:05, 25 March 2011 (UTC)
• Oppose WP:COMMONNAME makes this rather obvious. It might be an idea to ask rather than initiate a pointless RFC. Johnuniq (talk) 02:30, 26 March 2011 (UTC)
• Oppose "affect" vs "effect" 65.93.12.101 (talk) 02:41, 26 March 2011 (UTC)
• Oppose for the same reasons; call it what it's called. Dicklyon (talk) 04:42, 26 March 2011 (UTC)
• Oppose I have to say that, if the article were clearer on the modern meaning of the term 'centrifugal force', proposals like the above, based essentially on a misunderstanding, would not occur so easily. Martin Hogbin (talk) 10:56, 26 March 2011 (UTC)
• Strongly oppose: WP:COMMONNAME, wikt:affect vs wikt:effect. I guess the term "fictitious force" is fairly unhelpful and leads to this kind of thing as it seems to suggest that behaviour in non-inertial reference frames is somehow not "real", but I guess we're stuck with that too. Icalanise (talk) 14:47, 26 March 2011 (UTC)
• Oppose. "Simply construct Newton's Laws in a rotating system and you will see a centrifugal force term appear as plain as day." Powers ^T 23:26, 28 March 2011 (UTC)

The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Reactive centrifugal force - sometimes reaction to centripetal force is also centripetal

In the case of a 2 body system where two objects orbit in a circular path about a common center due to charge, gravity, or magnetism (or any attractive force that doesn't involve physical contact), the Newton third law pair of forces are both centripetal forces.

Change this example to one where two objects connected by a string move in a circular path about a common center and gravity is insignficant. In this case, the string exerts a centripetal force on the objects, and each object exerts a reactive centrifugal force on the end of the string.

So sometimes the reaction force to a centripetal force is reactive centrifugal force, and sometimes it's another centripetal force. I'm not sure how to address this in the main article. Rcgldr (talk) 04:31, 30 August 2011 (UTC)

I agree with your summary of the situation. At present, the article states the mass exerts an equal and opposite force on the object. This is the reactive centrifugal force. It is directed away from the center of rotation, and is exerted by the rotating mass on the object that originates the centripetal acceleration. The problem can be overcome by adding the following sentence immediately after the words centripetal acceleration.:

If the force on the mass derives from a gravitational field, an electric field or a magnetic field, the reactive centrifugal force acts on the field but it is customary to say that the equal and opposite force acts on the object responsible for the field. The mass, and the object responsible for the field, may be on opposite sides of the axis of rotation in which case both forces point towards the axis of rotation so both are centripetal. Dolphin (t) 07:52, 30 August 2011 (UTC)

Best drop 'reactive centrifugal force' altogether. It has never been of much used and it use today is frowned upon. It serves only to confuse. Martin Hogbin (talk) 16:35, 30 August 2011 (UTC)

As long as the qualifier reactive is used, I doubt there would be confusion. I thought the debate over the validity of the term reactive centrifugal force was over when it was added to this article and remains as a separate article. I just wanted to clarify that the reaction to centripetal acceleration may be a reactive centrifugal force, but not always. Rcgldr (talk) 17:33, 30 August 2011 (UTC)

There is no need for a special name for the reaction to the centripetal force it is just 'the reaction to the centripetal force'. We do not have a special name for the reaction to gravitational force when you stand on the ground because we do not need one, it is just the standard application of Newton's third law. Martin Hogbin (talk) 18:00, 30 August 2011 (UTC)

@Martin: But we do have a special name for the reaction to gravitational force when you stand on the ground - see Ground reaction force.

This thread is not about whether the article should use the expression reactive centrifugal force or the simpler centrifugal force. It is about how the article should acknowledge that in some circumstances the equal and opposite of a centripetal force is also a centripetal force. Dolphin (t) 22:30, 30 August 2011 (UTC)

But the ground contact force is not the reaction to any gravitational force. The reaction force to any gravitational force exerted by one body on another is the gravitational force exerted by that other body on the first. When two gravitating bodies are prevented by contact forces from following the trajectories dictated by their gravitational attraction alone, both bodies exert a contact force on the other, and these are reactive to each other.

David Wilson (talk · cont) 22:47, 30 August 2011 (UTC)

Yes, you are quite right, there are two pairs of forces exactly as you say.

My real point, however remains the same. Using the term 'centrifugal' for any force that happens to be outwardly directed is pointless and potentially confusing. Such usage is strongly discouraged in modern books on the subject. I am aware that historically the term 'centrifugal force' may have been used for things other than the inertial force required to do Newtonian physics in a rotating frame and that there may still be extant example of such usage but her are no sources advocating or promoting this usage.

Dolphin51's point is best addressed by only using 'centrifugal force' for the inertial force. The historical usage of the term should be moved to a section called 'Historical usage' or similar. The article as it is is endlessly confusing. Martin Hogbin (talk) 08:29, 31 August 2011 (UTC)

@Martin: I am interested in seeing some clarification of your comments. You have written Using … centrifugal for any force that … outwardly directed is pointless and potentially confusing. Am I correct in assuming this is your original research and not supported by anything authoritative in Wikipedia or elsewhere?

You have also written:

• there may still be extant example of such usage Yes, Wikipedia has an article Reactive centrifugal force. What do you propose for that article?
• there are no sources advocating or promoting this usage. The article Reactive centrifugal force cites “Inside Relativity” by Mook & Vargish

Even though Wikipedia aims to rely exclusively on reliable published sources, such sources will usually be far from unified in their presentations. Two reliable published sources on a common subject can present starkly differing views of how the world should be described. Wikipedia must grapple with these differing views and present them both in a way that isn’t contradictory. It is often a difficult task. It is usually not a solution for Wikipedia to present only one of those views and censor the other even though there will usually be some Users who advocate censorship as a means of achieving a simple, clear explanation. The articles on centrifugal force appears to be a perfect example of this contradiction. You seem to be in favor of censoring the view that centrifugal force can have a modern meaning – something akin to directed away from the axis of rotation. I favor acknowledging that this is a subject on which there are at least two views, and Wikipedia chooses to present both views. For example, you have written Such usage is strongly discouraged in modern books on the subject. I don’t doubt that there are books that strongly discourage such usage, but I doubt that all modern books discourage it. Are you able to write Such usage is strongly discouraged by all reliable published sources on the subject?

Your advocacy of your view relies significantly on denigrating certain elements of the article – you use the expressions pointless and potentially confusing and endlessly confusing. Expressions like this can be applied to anything at any time by anyone. Most people who read this Talk page are critical readers and are much more likely to be influenced by objective language than by the language of denigration

Even though the content of this thread is drifting away from the issue first raised by Rcgldr I am finding it rewarding and look forward to continuing the dialogue. Dolphin (t) 23:57, 31 August 2011 (UTC)

• After all this, I re-read the article and noticed the specific wording: provided by a centripetal force, which is exerted on the mass by some other object . Since it specifies an object that creates the centripetal force, and not a field, the wording of the article is fine, but perhaps it should describe the situation when a field is creating the force. Rcgldr (talk) 11:31, 1 September 2011 (UTC)

My view that using CF to mean anything other than the inertial force is confusing and unhelpful is the mainstream view of mathematicians and physicists on the subject. Have you read the text from the source that you quote? It is actually arguing the same thing as I am, that CF should be applied to the inertial force only. It refers to the reactive force as 'a centrifugal force', which of course it is, in common with any other force that happens to always act away from a centre. Martin Hogbin (talk) 18:05, 1 September 2011 (UTC)

That's an OK view, for the mainstream scientific guys as you note, but it denies what most people think of as CF -- like the force of a string pulling outward when they swing a weight around. There are other sources that talk about this reactive force. Dicklyon (talk) 07:36, 4 September 2011 (UTC)

[Inserted here due to edit conflict] Dick, I know we have discussed this before but let me try to convince you that alternative CF forces are a bad idea.

For people who are completely non-technical, that is to say they have no interest in the subject at all and no desire for any real degree of understanding, it might be OK to have some vague notion of a centrifugal force that pulls stuff to the outside in a spinning system. That is fine for people who do not understand what a force is and do not care. I doubt these people would be looking up the subject in WP and we should certainly not write the article specifically for them, although I have no objection to having a section on intuitive notions of CF along with historical meanings.

For anyone who wants to understand the subject at all, be they mathematician, engineer, physicist, or interested layman, the current view (I am sure I could find sources to support this if needed) is that it is best to work only in inertial frames and apply Newton's three laws. That is all that is needed in principle to solve any problem, there is no need for any mysterious forces.

I am aware that there will always be a reaction to the centripetal force. However, there is no advantage to giving this particular reaction force a special name, especially as that name will be used in more advanced work to mean something completely different. All forces have an equal and opposite reaction and we do not give them all names. Also, as Dolphin51 notes above, in, for example a Newtonian system of two mutually orbiting bodies, the reaction to the centripetal force on one body is not even centrifugally directed (unless we are drawn into a discussion about reaction against the gravitational field, which is not common in Newtonian gravitation).

Your example of the stone on a string gives a perfect example of how the unnecessary use of reactive CF can lead to pointless confusion. Using the concept of reactive CF, this is the line of reasoning we must follow:

We wish to move a stone in a circular path. We must therefore apply a centripetal force to the stone. We pull the string which pulls the stone. This creates a reaction force between the stone and the string which we call the reactive CF. This force acts on the string which causes a tension in the string. We feel this tension (not the CF) at the other end. If you think I am being deliberately confusing then please tell me how you would analyse this system using reactive CF. Martin Hogbin (talk) 09:37, 4 September 2011 (UTC)

@Martin: It seems to me that there are two different meanings applied to the expression centrifugal force. Some writers use centrifugal force to mean a fictitious force (or pseudo force or inertial force) directed away from the axis of rotation. Others use it to mean any real force that is always directed away from the axis of rotation. I have read pages 46 and 47 of Mook & Vargish and they use the expression in both ways, giving a rather contradictory impression.

On page 46 they say The third law also permits us to understand the fictional force commonly called centrifugal force. On page 47 they say But still we say that in the Newtonian view centrifugal force is fictitious. In these sentences M & V are using centrifugal force to mean a fictitious force.

However, M & V also apply the expression in a way that demonstrates its alternative meaning. On page 46 they say The force that that the ball seems to exert on the string to pull it taut is called a centrifugal force (meaning a force that acts to pull something away from the center.) In this sentence M & V are using centrifugal force to mean a force that is always directed away from the axis of rotation. Consequently, page 46 of M & V is a reasonable source to cite in our article Reactive centrifugal force.

Scientific writers use both meanings of the expression centrifugal force so I think it is reasonable for Wikipedia to contain information about both meanings, and also to focus on the fact that the two meanings are somewhat incompatible – one meaning a fictitious force and the other meaning a real force. Dolphin (t) 08:41, 4 September 2011 (UTC)

Dolphin, firstly see my reply to Dick above.

There is a fundamental difference in the two usages of CF. If we wish to use Newtonian physics unchanged in a rotating frame we find that we need to invent a number of (inertial) forces that have never existed before. One of these forces is the centrifugal force. It needs a special name because it is completely new to Newtonian physics and exists only because we have chosen to apply Newton's laws in a rotating frame as if it were an inertial frame. There is no obvious name for this force already.

The reactive CF is simply the reaction, according to Newton's third law, to the centripetal force we have applied to the object to accelerate it into a circular path. Such reaction forces are universal in Newtonian physics and they do not, in general, have or need special names.

Historically, CF has been used with a variety of meanings (some of them plain wrong by today's understanding of the subject) and we could, no doubt, find sources for several of them. However, our job, as editors of an encyclopedia is to explain the subject as it is currently used and taught. As I said above, I have no objection to a section on historical and intuitive meanings of CF, in fact this would be an excellent idea as it might reduce the confusion which, despite the best efforts of educators, still seems to surround this subject. Martin Hogbin (talk) 09:57, 4 September 2011 (UTC)

Inadvisable deletion leaves no clues to related topics

The recent deletion found here removes the historical background connecting centrifugal force with the basic question of how (or whether) absolute rotation is detectible. The basis for the deletion is that a more complete discussion of these topics can be found elsewhere (namely at the linked articles in the deleted material). One may question whether an introduction to a topic found in a more general article is supposed to be complete, or whether its role is rather one of introduction. In any case, the reader no longer is provided any links to this material and, of course, the brief introduction to prod the reader's imagination no longer is there. Likewise, those searching this article for this connection between centrifugal force and these historically important questions now will be unable to find them here. Brews ohare (talk) 18:32, 26 November 2011 (UTC)

I agree. I have restored the section (diff). I will contact FyzixFighter and suggest he joins this debate if he still thinks the erasure should be permanent. Dolphin (t) 20:47, 26 November 2011 (UTC)

Thanks Dolphin51 for the heads up. I still don't think the section belongs on this page, for a specific reason and a more general reason related to the purpose of this page. The specific reason is that the section in question only has specifically to do with the fictitious centrifugal force. I removed it because I was imo trying to reduce some information creep and try to keep some semblance of hierarchical organization, ie the most general topics here, and topics unique to only one of the subtopics on the subpages. If the argument is that there is a desire to keep the historical significance of that section, may I suggest summarizing the section a bit more and moving the information to the "History" section near the top.

But more generally, what is the purpose of this page, and does that purpose fit into WP policies and established style guidelines? It really can't be a disambiguation page in the sense that WP uses that distinction, because it doesn't follow WP:DAB or WP:MOSDAB. Personally I think the fictitious centrifugal force (the Centrifugal force (rotating reference frame)) satisfies both the usage and importance criteria for the primary topic, and so that page should be moved here (dropping the parenthetical) and a hatnote pointing to the reactive centrifugal force page. What are your thoughts on this idea, Dolphin51? --FyzixFighter (talk) 16:56, 27 November 2011 (UTC)

I've followed the suggestion to put a modification version of this summary section with the History sub-header. It serves the purpose of introducing the reader to a number of related WP articles that may interest them. Brews ohare (talk) 21:40, 27 November 2011 (UTC)

Figure of the Earth

Centrifugal force causes rotating planets to assume the shape of an oblate spheroid

The material about the figure of the Earth removed in this edit with the observation that "I don't see in the refs where it is connected to the absolute motion debate" is related to absolute rotation inasmuch as if the observer were rotating and not the Earth, the Earth would be spherical, not oblate. The explanation provided by Newton for the oblate figure was that centrifugal force being larger at the equator than at the pole pulled the mass of the Earth further from its axis at the equator. I am not sure whether this point was unclear to the deleting editor, or whether the objection was that it was inadequately referenced. If so desired, a reference to Principia can be added. Here is another source. This source places the rotating bucket experiment and the oblate figure of the Earth in the same paragraph. This source connects it directly to Newton's examples demonstrating absolute rotation. Brews ohare (talk) 05:59, 28 November 2011 (UTC)

I removed it because none of the refs that I had seen connected the material about the figure of the Earth directly as one of Newton's arguments about absolute rotation. All of the refs, including all but the last ref provided above, merely describe the oblate figure as a centrifugal force phenomenon. However, any phenomenon that is attributed to centrifugal force would work in the general formulation of Newton's argument, ie the effects are only seen in the frame where the object is not rotating if the frame itself is rotating with respect to absolute space. Nevertheless, the context of the edit in question is about the specific historical arguments that Newton used to argue for detecting absolute rotation and the privileged inertial frame where centrifugal force disappears. That's the connection that I did not see and generally still do not see in the provided references. However, like I said before, only that last ref provided above seems to come close to making that connection, but since it's only a snippet view, I'd like to look at the full reference to see if it's just the authors themselves or the authors presenting Newton's use of the oblate figure in the historical argument about absolute rotation and space. If anyone has the full text, perhaps they could enlighten us, otherwise I'll try to get full access to the text tomorrow. --FyzixFighter (talk) 07:08, 28 November 2011 (UTC)

After checking that source this morning, I don't believe it supports the statement that Newton used the oblate figure of the Earth (or any rotating spheroid) as evidence that absolute rotation can be detected/defined, not in the same sense that he used the bucket argument or the spinning orbs. --FyzixFighter (talk) 16:32, 28 November 2011 (UTC)

FyzixFighter: I believe you are right in saying that Newton did not introduce this matter directly as evidence of absolute rotation, at least not in the Principia where he directly discusses "true" vs. "relative" motion. In his discussion of the shape of the Earth, however, he makes the assumption of absolute rotation of the Earth the presupposition of his argument in Proposition XIX Problem 3: To find the proportion of the axis of a planet to the diameters perpendicular thereto. So from an historical viewpoint, Newton did not use this example directly, but he obviously did use the absolute rotation of the earth to find its figure. It seems historically accurate to say that Newton used the figure of the earth as a quantitative demonstration of the effects of absolute rotation, although he did not deem it a transparent example, but one that required a lengthy discussion to establish the facts to be explained. According to Melosh debate with Newton at the time over whether the Earth was indeed oblate led to an actual expedition to measure the Earth's oblateness. Brews ohare (talk) 18:28, 28 November 2011 (UTC)

This source states the matter succinctly. Brews ohare (talk) 18:59, 28 November 2011 (UTC)

If we separate this matter from history, we have this observation:Datta

Isn't the fact that the Earth is slightly thicker around the equator –making it look more like an oblate spheroid than a sphere– enough evidence that the earth is absolutely rotating? The necessary flattening force on the earth, known as centrifugal force, comes about only because the earth is turning. How can it originate if the earth is believed to be stationary and , instead the universe is made to revolve around? (page 5)

Apparently the oblate shapes of Jupiter and Saturn (much more noticeable than Earth) were noted in the 1600's, as reported by Isaac Asimov. In my mind, this example is so forceful that leaving it out of this article is a disservice to the reader. It should be retained in some fashion, if not as history, then as a striking example of the role of centrifugal force. Brews ohare (talk) 22:12, 28 November 2011 (UTC)

Animation

I've drawn some pictures for de.WP, which might be of interest for english language to. On request I'll change annotaion, but I don't know their conventions in other parts of the world.

Animation

Picture with annotation

Translated annotation

--Stündle (talk) 08:59, 26 September 2011 (UTC)

Nice work. However, without a more detailed explanation of the meanings of the symbols ${\stackrel {\rightarrow }{F}}_{Zf}$ and ${\stackrel {\rightarrow }{F}}_{C}$ I believe the lower half of the diagram on the right might be misleading. Presumably ${\stackrel {\rightarrow }{F}}_{Zf}$ denotes the centrifugal pseudoforce which apparently acts on the man on the revolving beam from the point of view of the rotating coordinate system. But what does ${\stackrel {\rightarrow }{F}}_{C}$ represent? Is it just the Coriolis pseudoforce apparently acting on the other man, or is it the total pseudoforce apparently acting on him—i.e. the resultant of the Coriolis and centrifugal pseudoforces. I believe it would be preferable to represent both of those pseudoforces on the diagram, with the latter, of course, acting radially outwards and having half the magnitude of the former.

David Wilson (talk · cont) 11:25, 26 September 2011 (UTC)

Annotation:

${\stackrel {\rightarrow }{F}}_{C}$: Coriolis force

${\stackrel {\rightarrow }{F}}_{Zf}$: Centrifugal force (Fictitious centrifugal force)

${\stackrel {\rightarrow }{F}}_{Zf}$: Centripetal force

${\stackrel {\rightarrow }{v}}_{B}$: velocity

${\stackrel {\rightarrow }{v}}_{B}'$: velocity seen from rotating reference frame

Red person is resting in a inertial frame

Green person is in a uniform rotating reference frame

$\omega =konst.$: rotation speed is constant

Actually I can't figure out what you are talking about. In germany I don't think there is something like total pseudoforce in use. These pictures refer to “Newton's laws of motion”. --Stündle (talk) 12:55, 26 September 2011 (UTC)

By "total pseudoforce" I simply mean the (vector) sum of all the pseudoforces apparently acting on a body. My point is that in the rotating reference frame in the bottom halves of your diagrams, the Coriolis pseudoforce Is not the only one apparently acting on the person in the red shirt. There is also an outwardly directed centrifugal pseudoforce apparently acting on him. The magnitude of the Coriolis pseudoforce is $2m\omega \mid \displaystyle {{\stackrel {\rightarrow }{v}}_{B}'}\mid =2m\omega ^{2}r$, where m is the mass of the person in the red shirt, and r is his distance from the centre of the beam. The magnitude of the centrifugal pseudoforce is $m\omega ^{2}r$. The (vector) sum of these two pseudoforces is a vector of magnitude $m\omega ^{2}r$ directed radially inwards, which is exactly the product of the red-shirted person's mass and his (apparent) acceleration (i.e. the acceleration of his coordinates in the rotating system).

David Wilson (talk · cont) 14:02, 26 September 2011 (UTC)

Well, I tried to translate and improve annotation of my picture. Results see above. --Stündle (talk) 07:30, 27 September 2011 (UTC)

It would also be better if the rotating chair was facing inwards. The poor chap must find it hard to stay in his seat as it is. Also, the distinction between lines representing forces and lines representing velocities should be clearer. Martin Hogbin (talk) 00:11, 14 January 2012 (UTC)

Where's the high school section

i got onto wikipedia to try to find out: if you spin a bucket on a string, given the weight, rate, and the length of the string: what's the force? I dare you to try and find out from Wikipedia without already having a thorough knowledge of the subject.

All the physics articles have this problem: they are all university level explanations of lagrangian mechanics, and any sections containing just the equations you need to solve basic problems actually get erased. Any complaint gets the answer "well, you can derive it from what's on the page", which completely misses the point.

Where's the centrifugal force page for the bottom 99%?

Paul Murray (talk) 23:18, 10 October 2011 (UTC)

It's a fair point, but the reason why anything is on Wikipedia is because someone cared enough about its absence to write it. If this is you, then...

This article doesn't need to be readable in its entirety by 99% of the audience, but some sections of it should be, it should be clear which these sections are, and reading these sections should be sufficient to answer their questions. I don't see this as a reason to remove the Langrangian, or to have a separate article without, but there's certainly scope for improving the readability of some other sections. Andy Dingley (talk) 00:14, 11 October 2011 (UTC)

Paul has made a valid point. Wikipedia has some valuable guidelines at WP:Make technical articles understandable.

At the beginning of every technical article there should be information that is understandable to young people, and people who are new to the field. After that, there should be a progressive increase in the level of complexity. Dolphin (t) 02:36, 11 October 2011 (UTC)

This is a summary-style article that's supposed to help you find the article you want, but people have a tendency to keep making it more complicated. Probably what you're looking for is the first equation in Centripetal force. Dicklyon (talk) 02:56, 11 October 2011 (UTC)

Dick, good to see you back. I responded to your comments on this subject on my talk page. Martin Hogbin (talk) 08:11, 11 October 2011 (UTC)

@Paul, when you say 'what is the force?', what force exactly do you mean? Martin Hogbin (talk) 08:29, 11 October 2011 (UTC)

Paul's question can be made more meaningful if re-worded to say What is the tension (or tensile force) in the string?Dolphin (t) 06:41, 10 January 2012 (UTC)

Yes, if we assume that that is what Paul meant. What is particularly unhelpful to beginners (and pointless for experts) is to have one name for several different things. Martin Hogbin (talk) 09:26, 10 January 2012 (UTC)

I can't see anything else that Paul could have meant. What one name for several different things do you have in mind? Dolphin (t) 12:40, 10 January 2012 (UTC)

Paul just says, "what's the force?". Does he mean, the 'Fictitious centrifugal force, acting in the water and bucket, the 'Reactive centrifugal force' exerted by the bucket on the string, or is he contemplating using Lagrangian mechanics? I fully understand why he finds the subject confusing. Martin Hogbin (talk) 16:39, 10 January 2012 (UTC)

Images

Forces on a ball in circular motion as seen in the inertial frame where the ball is seen to rotate (center) and as seen in a co-rotating frame where the ball appears stationary (right).

A ball in circular motion has a centripetal force on it; in the case of that force being applied by a massless string, the reaction force is an equal force, centrifugally directed, on the string, and via the string tension on the post holding the string.

Forces on a ball and a string keeping it in circular motion. Left: inertial frame where the ball is seen to rotate. Right: co-rotating frame where the ball appears stationary. Forces on the ball at center, forces placing the string under tension shown separately below.

Perhaps we need a diagram and a discussion of this example? Here's a diagram that might be used to show the centrifugal force and the reactive centrifugal force. The explanation accompanying the figure could be:

In the inertial frame the ball is subject to the centripetal force provided by the string tension, and the string (below) is subject to the reactive centrifugal force and the force due to the center-post which is the same as the centripetal force on the ball. In the co-rotating frame the ball appears stationary with zero net force because the string tension is balanced by the centrifugal force, and the string is subject to the same tensional forces seen by the inertial observers.

Formulas could also be provided? Brews ohare (talk) 18:23, 10 January 2012 (UTC)

I have added this material. Brews ohare (talk) 15:56, 11 January 2012 (UTC)

The figure is about as clear as mud; can anyone but Brews get info out of them? The annotations rotating and stationary are opposite to what would be applied to the frames of reference, so you need a lot of text to interpret that. The upper-left bit is not needed. And why do we want to talk about a reactive CF in a rotating frame? Dicklyon (talk) 18:51, 11 January 2012 (UTC)

I have to agree: the image tries to cram far too much into a small space, losing some important details as it does. It also is far to abstract for an 'example', while the use of colours is just confusing and will render the diagram useless for someone with poor colour vision or using a non-colour display. I doubt this is fixable without making the diagram too big. Perhaps because of this the text makes no sense: what co-rotating frame, what observers? So generally as an "Example" the whole section seems very abstract and unclear.--JohnBlackburne^words_deeds 19:54, 11 January 2012 (UTC)

Dick and Blackburne: You all haven't provided much guidance on how to improve the figure; just rained on the parade. What details are lacking? What isn't clear? For example, is it unclear that the centripetal force is inward? Is it unclear that the string is under tension? Is it unclear that the centrifugal force is outward? Would the arrows be indistinguishable on a gray scale for the colorblind? Would it be an improvement to have a blank space above the labeling of the arrows instead of a picture?

In the frame of the moving ball, the force on the string is the reaction against the string's pull on the ball to provide centripetal force, and is called "reactive centrifugal force". In the frame where the ball is stationary, the force on the string is again the reaction to the pull supplied by the string, this time to counter the centrifugal force on the ball. Both have the same size and direction, and the same origin, being due to the "action and reaction" Newton's law. The string is under the same forces in either frame. Are we to call the force on the end of the string by a different name in the two identical situations despite their being identical in every respect? . Maybe if it acts like a duck and quacks like a duck...?? Brews ohare (talk) 00:01, 12 January 2012 (UTC)

Have you both read the added section? I believe any confusion about the diagram is resolved if you read the text on the Main page that accompanies the figure. Brews ohare (talk) 05:47, 12 January 2012 (UTC)

I replaced it with a less complicated figure. It's perhaps not ideal, but it's better. Dicklyon (talk) 06:19, 12 January 2012 (UTC)

Hi Dick: I am glad to see you engage in improving the figure. Here are some shortcomings of the new figure:

1. The font is so small that it cannot be read. A larger font could be used if the wording were shortened. For example, it is not necessary to say on the figure that the post is immovable, or that the string is massless.
2. The linewidths are too lightweight for good visibility.
3. The normal understanding is that the centrifugal force acts outwardly upon the ball, but the figure labels instead the force at the post.
4. A reactive force generally is considered to arise at the point of application of the force to which it is a reaction. Thus, having the reactive force at the post, while the force causing the reaction is at the ball is contrary to normal practice.
5. Because only one circle is used to describe both the inertial and the co-rotating frames, it is made to appear that all three forces: centrifugal, centripetal, and the reactive centrifugal forces, are present in all frames. Only the reactive centrifugal force is present in all frames.

I hope that some improvements along these lines can be made. Brews ohare (talk) 15:36, 12 January 2012 (UTC)

I've submitted another alternative here. Brews ohare (talk) 17:03, 12 January 2012 (UTC)

It's not exactly a new figure, but was created almost a year ago. I agree the text is a bit small, but only a bit – it seems to be optimised for viewing at the default size of 300px. It's still easily readable at 200px, except for the red text being both coloured and inclined. But as it's an SVG that's easily fixed.

I don't see any other problems with it. The lines and arrows are clear and visible, the string goes from the ball to the post as it should. The centrifugal force acts both on the ball and the post, so is correctly placed.

As for adding more circles it seems likely that will just make it more confusing. The circles will have to be smaller making existing captions less clear and requiring even more detail and more text so it's clear what they signify. Someone could try adapting this but I would not encourage anyone trying as I can't see how it can be done.--JohnBlackburne^words_deeds 17:05, 12 January 2012 (UTC)

I've retouched the SVG file to make the text larger and clearer, using a darker colour for the coloured text, and editing a couple of things for length.--JohnBlackburne^words_deeds 17:20, 12 January 2012 (UTC)

I've broken out this thread about the images. At 200px the single-circle figure is legible. The alternative showing the inertial and co-rotating frames separately also is very clear at this size, and even at a smaller size. In my opinion treating the two frames on a single circle is not a clear approach because different forces are present in the two frames, and the single circle makes it look like all forces are present in both frames of reference. Brews ohare (talk) 17:32, 12 January 2012 (UTC)

In addition, it is not possible to show the reactive centrifugal force at its correct point of application on the ball-end of the string without making an exploded view. Brews ohare (talk) 17:35, 12 January 2012 (UTC)

I'm afraid the new image has most of the problems of the previous 5-circle image. It is really unclear what's going on: even if you know what it's trying to show it takes some time looking at it before you work out what it's meant to be showing, and we can't assume readers will have that knowledge. What does it mean 'stationary ball' ? Only one circle is labelled as "Rotating Ball", but only one, a different one, has an arrow that indicates it's turning. There is no indication what the colours mean, though presumably they are significant. No indication these are force at all ("Post"?) I am still unconvinced this can be done in a reasonable space with multiple rings. I certainly can't think how I'd do it, and both images here with five rings show how difficult it is.--JohnBlackburne^words_deeds 22:37, 12 January 2012 (UTC)

John: Thanks for trying to make clear what the problems are here. The diagram is organized in two columns and three rows. The left column is "rotating ball" and the right column is "stationary ball". So the bottom labels refer to columns, not solely the diagram immediately above. The colors simply connect the label of a particular color with the arrow of the same color. I am a bit bewildered that "stationary ball" is a confusing label. Do you have some further suggestions? Brews ohare (talk) 23:30, 12 January 2012 (UTC)

I've changed the figure slightly to emphasize the column organization and changed the labels of the columns to refer to frames. The label "post" has been changed to "post reaction". Any better? Brews ohare (talk) 23:59, 12 January 2012 (UTC)

The main problem you are trying to do too much in a small space: it still looks like a cluttered mess with the individual elements too similar, the colours and text labels confusing and it being unclear what's being represented. Even something simple like is it five things, five views of one thing, or something inbetween? As I noted above I don't think its any particular failing of your art, it's that you're trying to do the impossible.--JohnBlackburne^words_deeds 00:14, 13 January 2012 (UTC)

It doesn't sound like breaking it up into more figures would make you happier, eh? Brews ohare (talk) 01:38, 13 January 2012 (UTC)

I revised the labeling to mitigate the clutter a bit. Brews ohare (talk) 12:50, 13 January 2012 (UTC)

Brews, I know from experience that it would be more than a full-time job to try to moderate your aggressive rapid-fire nonstop editing. If you could work on making the article more concise, well sourced, and correct, that would be a huge benefit, in my opinion, compared to your usual adding of more fluffy-looking hard-to-interpret diagrams, examples, essays, and general bloat. I don't have time for this. Good luck to you guys. Dicklyon (talk) 16:41, 13 January 2012 (UTC)

Dick: Probably the balance between being concise and being clear will strike different contributors differently. For one thing, the audience conceived by one author is different than that of another. The addition of this example was in response to a legitimate reader complaint, and it was my hope that this example would prove helpful. Constructing an intuitively obvious diagram is difficult, and I understand that you are repulsed by the free body diagram common in engineering mechanics. The present image requires too much attention from the reader, but it's OK, it's accurate, it fits the explanation in the text. Your characterization of my contributions in general as pretty much worthless is not constructive, Dick, and I don't think it is objective. Brews ohare (talk) 18:49, 13 January 2012 (UTC)

Meaning of centrifugal force

Dick, I hope you will eventually come round to my way of thinking that this article should concentrate on meaning of CF that is almost universally taught and used by mathematicians, physicists, and engineers today. That would make it much simpler to understand. Martin Hogbin (talk) 18:21, 13 January 2012 (UTC)

Martin: I don't think your concept of restricting the article to the single version of centrifugal force called here the "fictitious centrifugal force" is responsive to the history of these WP articles. If you look back over the morass of Talk page episodes and Main page edits you will find that many readers use the term "centrifugal force" to mean "reactive centrifugal force". You will find that usage even in textbooks. You also will find in the history of these WP articles that many readers believe that centrifugal force means the Lagrangian "generalized centrifugal force" and that opinion also is found in textbooks. So, in my view, a general article on Centrifugal force should cover all these readers' expectations, and hopefully will widen their view to see that there are several usages that are related, but not identical, and that none can claim to be the centrifugal force. By including all the usages, maybe WP can avoid repeating the long exchanges of the past that result primarily because each reader tends to take their own view as the view and the other views as those of the great unwashed that need to wake up to the one true meaning. Brews ohare (talk) 18:39, 13 January 2012 (UTC)

I am happy to mention historical meanings of the term but today it is almost universally used with one meaning only. That is not a decision I have made, it is how things are. WP should reflect that. Nobody (well in infinitesimal specialist minority) uses the term CF to primarily refer to a Lagrangian "generalized centrifugal force" . Martin Hogbin (talk) 20:10, 13 January 2012 (UTC)

Martin: The above remarks about the meanings of "centrifugal force" are not historical curiosities, but are found in use today. You might take the time to look at the Lagrangian sources mentioned here. Some discussions are just a bit murky, like this, where the term centrifugal reaction is coined, and this one and this one where the reactive centrifugal force is called the centrifugal force. Brews ohare (talk) 23:22, 13 January 2012 (UTC)

Yes, I know that you can find the odd example where the reactive centrifugal force is used but this confusing and unnecessary usage of the term is strongly discouraged by most current educational sources. Martin Hogbin (talk) 00:02, 14 January 2012 (UTC)

As shown by the extended debates in the Talk pages here on WP, ignoring some usages doesn't make things easier on WP. Editors come to WP with their ideas as a first prejudice, and they won't go away. If a visitor finds their view of "centrifugal force" is not present, they'll add it to the main page. (They may even replace the meaning already on the main page because they think it's wrong.) Then a "simplifier" or a believer that only the "commonly accepted" view should be presented, and other views are "bloat", will revert the addition. And away we go.

As you know, reading about various views at the outset is an easier form of persuasion than pushing only one view on the article Main page and ending up debating what is the "real" meaning on Talk pages all over again. And again. And with sources to support all the opinions, which all have adherents in the published record. And is your source better than my source? And on, and on.

It's stretching things to say presenting different usages is confusing and unnecessary - it's just becoming aware there is a variety of things denoted by the technical term "centrifugal force" before confrontation erupts on a Talk page over a revert of one's edit adding your take. Brews ohare (talk) 04:52, 14 January 2012 (UTC)

Lagrangian version of generalized centrifugal forces

FyzixFighter, your revision here was not correct. For more detail about the Lagrangian version, please look at the discussion later in the article and also in this subsection of another article. I believe these sections are accurate. In particular, please look at the boxed quotation in the latter section by Ge et al..

The situation is somewhat like this: the Lagrangian approach is based upon generalized coordinates and the generalized forces are related to the time derivatives of these coordinates. As such, these forces need have no connection with forces as defined in Newton's laws, although sometimes there is a correspondence. In particular, the so-called "centrifugal forces" referred to for example in the field of robotics is normally not a force from Newton's standpoint at all. An exception is the case of polar coordinates as discussed explicitly, where it happens that the the Lagrangian approach results in the same equations as Newton's laws in a co-rotating frame. This example is unusual however, as is explained at the above links. Brews ohare (talk) 05:36, 10 January 2012 (UTC)

It is not the case that the Lagrangian approach is more general than the Newtonian approach, and the generalized forces do not include the Newtonian vector forces as a special case. The interpretations of the two methods do sometimes overlap, but mostly they are disjoint, and not all Newtonian forces are generalized forces, nor vice versa. Brews ohare (talk) 05:40, 10 January 2012 (UTC)

I'm sorry but I disagree. The description of the three contexts are almost taken directly from the Bini et al 1997 reference. Bini's third context is not tied to the Newtonian approach, although as you note there is correspondence. In the original text that I reverted to, the wording does not limit it to a Newtonian approach so most of your argument above is against a point that neither I or the original text is making. Again, I'm basing this on my reading of the Bini reference which I believe includes but is not limited to the Lagrangian usage, so I don't think it is OR and it is well supported by a reliable source. This text has stood a while as it is, so let's discuss and get consensus since your edit was challenged (per WP:BRD) rather than set off an edit war. --FyzixFighter (talk) 06:00, 10 January 2012 (UTC)

I don't see why this context is mentioned at all. There's a whole separate section for the generalized fictitious forces in Lagrangian mechanics. Few sources mix up "fictitious centrifugal force" with these. Here is the diff from April 2010 where it went from being a brief mention and ref to the section below to the beginning of bloat. How about we put it back to that brief mention? Dicklyon (talk) 06:02, 10 January 2012 (UTC)

We agree on this one Dick. We have already had one complaint that the article is incomprehensible. Martin Hogbin (talk) 22:53, 10 January 2012 (UTC)

Hi Fyzix: The links to the Bini reference are not working for me, so I cannot read what these authors actually said.

The references cited in the two WP sections I have linked above are quite clear. In particular, the "centrifugal forces" of the robotics engineers are simply the squared q-dot terms, and are not Newtonian forces except in the special case of polar coordinates.

In my view the statement "The third context is the most general, and subsumes the first two, as well as stationary curved coordinates (e.g., polar coordinates)..." is quite incorrect. First, Lagrangian and Newtonian mechanics are entirely equivalent within classical mechanics, so this statement cannot mean that Lagrangian mechanics is more general. Second, the article is about centrifugal force, so it is natural to assume that is the subject under discussion. In this arena of centrifugal force it is more correct to say that Lagrangian generalized centrifugal force is unrelated to Newtonian centrifugal force, with perhaps one exceptional case where they overlap. One confusion in comparing Lagrangian centrifugal forces to those of Newton is that these forces do not disappear in an inertial frame of reference, as inertial forces are supposed to do under the Newtonian concepts.

If I have misinterpreted the paragraph, it should be rephrased to say what is meant. Brews ohare (talk) 06:32, 10 January 2012 (UTC)

I'd go so far as to say that if the formulation you have proposed, Fyzix, is adopted, in my opinion it contradicts the following sub-section in this article and the more extended discussion of the other article as linked above. Brews ohare (talk) 06:45, 10 January 2012 (UTC)

I have managed to locate the Bini references and have updated these links. These authors' discussion on p. 5 does not support the language that I've removed. Brews ohare (talk) 15:16, 10 January 2012 (UTC)

To DickLyon: The reason for bringing up the Lagrangian ideas is the following: First, the two come up all the time with both being called simply "centrifugal forces" and this confusion of terminology has led in the past to very prolonged confusion because the inertial forces of Newton disappear in an inertial frame, while the generalized centrifugal forces do not. This article is an opportunity to set the the distinction forward. Second, the Lagrangian generalized centrifugal force is very commonly used in several branches of physics and engineering, particularity in robotics, so a reader might well google this article looking for some illumination on this usage. Brews ohare (talk) 06:32, 10 January 2012 (UTC)

Dick, perhaps your support for including reactive centrifugal force has bearing here? Brews ohare (talk) 14:59, 10 January 2012 (UTC)

I'd support a return to this formulation, which as you say precedes the introduction of "bloat". Brews ohare (talk) 16:28, 10 January 2012 (UTC)

The Bini reference is about general relativity. This article is about, or should be about, Newtonian physics. Martin Hogbin (talk) 22:59, 10 January 2012 (UTC)

Martin: I think you have to actually read the article and not just go by its title. Brews ohare (talk) 23:26, 10 January 2012 (UTC)

Putting the terminology aside and focusing on the physics: as the section now reads it's bit misleading, because if you want, you can also switch to a co-rotating frame and derive the expression for centrifugal force, coriolis force etc. Count Iblis (talk) 22:58, 10 January 2012 (UTC)

Count: You can switch to a co-rotating frame in simple systems, but the term "centrifugal force" is applied to the q-dot squared terms in complex systems where there is no frame that co-rotates with all the spinning elements of the system, which rotate about many individual centers. Brews ohare (talk) 23:26, 10 January 2012 (UTC)

Where is the high-school section? (Part II)

To return to the title of the above thread: Where is the high-school section? This is an important general question and runs into the balance between the accessibility of WP to the nonspecialist and the guidelines like WP is not a textbook. Simple examples with the associated math are an anathema to some editors like Dicklyon who invokes his concepts of "bloat" and "symbol soup" and has drastically cut examples from this article, and not just those with formulas, but those with qualitative points and diagrams to boot.

Possibly it is time to lay out a formal set of classifications for articles into, for example, "Broad introductions", "High-school treatments", "Undergraduate treatments" and "Specialist discussions". In the last category are a great many treatments of mathematical topics on WP that I find incomprehensible myself despite a PhD in solid-state physics and having published articles of my own in Physical Review on the application of space groups to crystalline phase transitions. Brews ohare (talk) 15:51, 10 January 2012 (UTC)

We already have beginnings of such a system without formal introduction in having articles like Quantum mechanics & Introduction to quantum mechanics & Particle in a box & Quantum harmonic oscillator, and also Theory of relativity & Special relativity & Introduction to special relativity. The recasting of the criteria applicable to such categories is nowhere stated, to my knowledge. Brews ohare (talk) 16:00, 10 January 2012 (UTC)

I suggest that you reduce the instance of the motion of a chair on a revolving carriage to an instantaneous image of the support pivot and the hanging chain and the chair, while rotating and ask for an explanation of what you see. You see a chain hanging at an angle from a support due to a downward gravitational force, yes? But you see the chair offset from the downward direction. And how are you going to explain that? Well the instantaneous motion is straight ahead, so no force is involved there. But the forward motion is restricted in direction by the inertial characteristic of the tether which would have to lengthen in order for the chair to continue straight ahead. And this process continues until the force in the tether achieves a direction toward the center of the radius of rotation. But this results in the level of the chair being raised by a force in the tether that raises the chair against the force of gravity. And what is that force? It has to be a force at right angles to the direction of the chair, otherwise the chair would slow down. So it has to be a portion of the force of inertia that is related to the rate of motion of the chair and contents. And since the only other thing that is related to the that rate of motion is the kinetic energy of the chair and contents. And so we have the value mv^2/2 being related to the value mr^2, and so we wind up with r being proportional to v times the square root of 1/2. So the centrifugal force as a concept can be said to be a part of the force of inertia related to the circumstance of circular motion.WFPM (talk) 21:30, 27 February 2012 (UTC)

Classical mechanics panel

I have removed the classical mechanics panel at the top of this article to see what others think.

To my mind it is completely out of character with the rest of Wikipedia. Martin Hogbin (talk) 23:28, 27 February 2012 (UTC)

I checked a few of the other articles on classic mechanics - Centripetal force, Friction and some others and most of them had this panel at the top of the article. I agree it appears to be inconsistent to have it at the top of the article. Many articles have a panel of this kind at the bottom of the article. Even today's Featured Article Murasaki Shikibu has a panel at the bottom. It is very common to have the panel, but it should be at the bottom, not near the top. Dolphin (t) 06:38, 28 February 2012 (UTC)

That seems to be a good solution to me. Martin Hogbin (talk) 09:28, 28 February 2012 (UTC)

I think that the page-wide header is actually some kind of bug, but I could be wrong. It used to just be a sidebar at the top left of the page (see how it appears at template:Classical mechanics). For some reason the expansion of the sublist is what is causing the template to expand all the way horizontally. If I recall correctly, it used to be that the sidebar width remained the same when the sublist was expanded, so my guess is someone messed with the parent template somehow. --FyzixFighter (talk) 15:02, 28 February 2012 (UTC)

It was missing a width; probably that was in the template it was previously based on but which was deleted. I've added a width back in. Still not sure it belongs though, as it contains far too many links to be useful for navigation.--JohnBlackburne^words_deeds 15:41, 28 February 2012 (UTC)

Centrifical Force

Where is the mention of "centrifical force"? That is how I got here by searching for the word "centifical". Millions of students were taught this phrase in the past, apparently incorrectly. Funny how dictionaries decided common usage did not dictate "centifical" as a proper word, in this case. The term should be mentioned in the article as incorrect usage etc... since it's search reults in this article. Can somebody add a mention of it? 99.251.114.120 (talk) 14:40, 13 March 2012 (UTC)

I've never heard of it before but it looks like a misspelling. The reason a search for it lists this article highly is Google assumes it's a misspelling and so tries it's closest match among likely searches. A search for "centrifocal force", and "centrifecal force" both list this article first for the same reason, even though I've just made up those words.--JohnBlackburne^words_deeds 15:01, 13 March 2012 (UTC)

I think the word is a common misspelling/mispronunciation of 'centrifugal'. Martin Hogbin (talk) 15:47, 13 March 2012 (UTC)

This has come up before. Until the misspelling becomes sufficiently common to be mentioned in a mainstream dictionary or respected style guide, I don't see how Wikipedia's policies on undue weight and original research could be interpreted as allowing the term to be used or referred to in any of its articles.

David Wilson (talk · cont) 02:48, 14 March 2012 (UTC)

Sometimes we make redirects from misspellings. Would that make sense here? Dicklyon (talk) 03:02, 14 March 2012 (UTC)

Yes, there are two re-directs based on misspellings - Centrafugal and Centrifical force. Dolphin (t) 03:09, 14 March 2012 (UTC)

Some references to this misspelling claim it has been seen, frequently in documents since the 1850s. I was taught this as a correct term in my school science lessons and many have experienced the same. I suspect it was a very common error in the 1900s. Try a search for the term and you will find websites and forums that believe it is a proper word. 99.251.114.120 (talk) 04:03, 14 March 2012 (UTC)

I support the redirect and also suggest that we add something like 'also known informally as centrifical force' to the lead. Martin Hogbin (talk) 09:23, 14 March 2012 (UTC)

Done but I don't like the way it looks (format) 99.251.114.120 (talk) 15:10, 15 March 2012 (UTC)

Looks like somebody didn't want it stating it was unsourced material, without discussion. 99.251.114.120 (talk) 15:21, 15 March 2012 (UTC)

Frankly, I do not see any consensus on putting a note on top of the page; the only consensus reached was to make the redirects. All misspellings are unsourced and in addition "centrifocal" was just invented. At that point we should list all common misspellings on any article which would be absurd. --Mark91it's my world 15:39, 15 March 2012 (UTC)

No consensus was implied for "on top of the page" and I may have gotten carried away with inclusions. I couldn't find a better place and it belongs with the other clarification issue (centripedal). Yes, the absurdity of quantity could become an issue for all the imagined spellings. "Centrifical", a very common mispronounciation and spelling, in North America but may be regional in nature. I guess this needs to addressed with higher policy makers about the redirection process notes to clarify what is happpening to users (remember them?) 99.251.114.120 (talk) 16:51, 15 March 2012 (UTC)

'Centrifical' is a common misspelling/mispronunciation of 'centrifugal'; just Google it. I have heard it used in the UK so I do not think it is s regional US thing. It is usual to put alternative spellings in the lead with just a brief note (maybe , 'sometimes informally called centrifical'). I think the other misspellings are much rarer and not worthy of note in the lead. Martin Hogbin (talk) 18:07, 15 March 2012 (UTC)

'Centrifical force" is a misspelling that shouldn't require any sources. What would I reference? Another dictionary saying it is commonly mispelled? The argument is nonsense and the misspelling should be mentioned in the article for the public's information. Is wikipedia a source of information the public might want to know? Wikipedia, itself recognizes the term internally by it's redirecting of the misspelled term and even being used, ignorantly, inside some wikipedia articles. 98% of wikipedia has no references. Are we seeing some WP:Ownership here? — Preceding unsigned comment added by 99.236.126.209 (talk) 01:44, 16 March 2012 (UTC)

The other spellings were made up earlier in this thread (I did search and got zero hits for both). As for 'centrifical' it would be good to know where it comes from or where it's used. It could be a regional spelling/pronunciation variation in which case it might be better covered by an article on such variations or even on a particular dialect.--JohnBlackburne^words_deeds 01:50, 16 March 2012 (UTC)

Here's a source which simply lists "centrifical" as a frequent misspelling of "centrifugal". So if anyone wants to add a note to the article to that effect, it's certainly possible to do it without indulging in "original research". In my opinion, this would best be done with a footnote.

David Wilson (talk · cont) 09:42, 16 March 2012 (UTC)

I agree that we do not really need a reference but seeing as you have found a nice one I suggest that we add it. Do you have more details, page number for example? Martin Hogbin (talk) 13:28, 16 March 2012 (UTC)

I have added the term to the lead with ref. Maybe 'erroneously' would be better than 'informally'. Martin Hogbin (talk) 13:52, 16 March 2012 (UTC)

A footnote is not the place for this because people who are wondering about that name will never think of looking there. See Wikipedia:Manual_of_Style/Lead_section#Alternative_names.

But "centrifical force" is simply an erroneous spelling, not an "alternative name"', so I can't see how the Manual of Style on the latter applies. Nevertheless, I'm not sufficiently bothered by the issue to further argue the toss.

David Wilson (talk · cont) 16:30, 16 March 2012 (UTC)

I agree. I don't think that this is covered by the section of MOS dealing with alternative names. Perhaps misspellings should be mentioned if notable but I don't think this misspelling is notable enough and certainly I don't think it belongs in the lead. Δρ.Κ. ^{λόγοςπράξις} 16:54, 16 March 2012 (UTC)

Have you Googled it? It is a very common misspelling and some people may want to know what it means. Look at the top of this section and see the comments from 99.251.114.120.. Martin Hogbin (talk) 17:46, 16 March 2012 (UTC)

Please don't be presumptuous. Of course I looked at the top of the section and read the whole exchange. But I am not convinced. First, I think that googling for the term and reaching your own conclusions constitutes original research. Second, the citation at the lead is just one instance where this term is found in a somewhat reliable source. Are there any other dictionaries which mention the term? If not, I suggest that evidence of the notability of this term based on reliable sources is lacking. Therefore inclusion in the article may be WP:UNDUE weight. Adding it to the lead is currently unsupportable. Δρ.Κ. ^{λόγοςπράξις} 18:32, 16 March 2012 (UTC)

Perhaps you should also review David Wilson's comments near the top of the section where he essentially makes the same points as I do about undue weight and original research. This was already apparent in the lead by the use of the weasel word "sometimes" which I removed once, but somehow it got reinstated. The weasel word "sometimes" is a sure indicator of original research. It is also not surprising that it is not supported by the citation used. Δρ.Κ. ^{λόγοςπράξις} 19:03, 16 March 2012 (UTC)

We could perhaps reference a book like this one that includes it in a list of "frequently misspelled words"? Oh, I see that was tried already... Dicklyon (talk) 19:23, 16 March 2012 (UTC)

Is this not all pretty silly? There are a boatload more Google hits for "Brett Farve" than for "Centrfical force," but you don't see the article on Brett Favre starting off with a discussion of ways people misspell his name. Google prompts searchers with the correct spelling in both cases; Wikipedia redirects to the appropriate article in both cases. That is as it should be. Further belaboring the point serves no purpose I can see. Rracecarr (talk) 19:55, 16 March 2012 (UTC)

I agree. Δρ.Κ. ^{λόγοςπράξις} 20:21, 16 March 2012 (UTC)

Rracecarr, have a look at the links you get when you Google Brett Farve. You will see that they nearly all have the correct spelling. This effect has already been noted above, Google tries to find misspelled words. Now try it with 'centrifical' and you will see that all the links actually include the word 'centrifical', some of them reasonably reliable sources. It is not a simple spelling or typo it is a word that is commonly used. Martin Hogbin (talk) 22:45, 16 March 2012 (UTC)

False. The links have the incorrect spelling. Google corrects the spelling the first time you search, but it offers you a link: "search instead for Brett Farve". Click it. 8 million hits. Rracecarr (talk) 05:04, 17 March 2012 (UTC)

I do not know which Google you are using but when I do a search for "Brett Farve" and confirm that I mean it to be spelled like that I get 'About 571,000 results'. When I actually look at the links I see that the majority (6/11 on the first page) still have the correct spelling in them. I presume that the articles mention the incorrect spelling (probably in the tags) to ensure that they get hits from misspellers.

'Centrifical' is completely different, just take a look. On the first page all the links use the word 'centrifical'. It is quite clear from reading them that they all believe that 'centrifical force' exists or at least they show that it is a word in common use. Worse than that, some of the links seem to indicate that 'centrifical' and 'centrifugal' are two different forces. This misunderstanding is something that this article could and should clear up for the benefit of our readers.

'Centrifical' is not a misspelling, it is not quite a misnoner, perhaps it could best be described as a common Malapropism. We have the opportunity to clarify things. Martin Hogbin (talk) 10:00, 17 March 2012 (UTC)

I get "about 8,590,000 results" for Brett Farve: [6]. All of them appear to have the spelling Farve in them (many also have the name spelled correctly). That is why they turn up in the results. Regardless, the job of this article is to provide verifiable information about centrifugal force. If, as you claim, it is not simply a (marginally) common spelling error, and you want to include anything about centrifical force, it seems to me you need a reliable source stating that a significant number of people believe there is such a thing, separate from centrifugal force. It is not enough to point to references which get it wrong--that is OR. Rracecarr (talk) 20:41, 17 March 2012 (UTC)

I see you have removed the name based on the above misunderstanding. This means that anyone who looks up the term 'centrifical' will now be unsure as to what it means. All you have done is to make the article less useful to readers who may be in doubt. Martin Hogbin (talk) 22:50, 16 March 2012 (UTC)

It doesn't mean anything: it's a spelling error. The source, a book of spelling errors, confirms that. We usually have redirects from common misspellings (and one exists in this case) but it's not usual to put them in an article.--JohnBlackburne^words_deeds 23:03, 16 March 2012 (UTC)

After thinking over this, I have to agree that including details about any common misspelling of the article title in the article itself would be according it too much weight. The purpose of the article is (or, in my opinion, should be) to provide an explanation of what centrifugal force is, not to give spelling lessons. Moreover, "centrifical force" is just one of several common misspellings of "centrifugal force". If google is to be believed, it may not even be the most common. Google gives around 123,000 English page hits for "centrifigal force" as opposed to only 52,400 for "centrifical force", though the order is reversed for google English book hits—729 for "centrifical force" as opposed to only 103 for "centrifigal force". Other reasonably common misspellings, with their google English page hits and google English book hits in parentheses, are: "centrafugal force" (31,400, 20), "centrifiugal force" (14,500, 26), "centrefugal force" (13,400, 68), and "centrufugal force" (11,300, 20).

I do see Martin Hogbin's point, though: disabusing readers of erroneous ideas about spelling is a perfectly useful and reasonable thing to want to do—provided it can be done without cluttering up the article with information that's practically useless for those who already know how to spell. I believe there's a way of doing this which may be an acceptable compromise—namely, by replacing the hard redirect at Centrifical force with a soft redirect and putting the information about the misspelling on that page instead. I have done this for the page Centrifical force as an illustration. Anyone who thinks this is a really bad idea should feel free to revert.

David Wilson (talk · cont) 00:53, 17 March 2012 (UTC)

A bad idea and very non-standard. Soft redirects are meant for links between projects, not for misspellings for which we have {{R from misspelling}}. I will leave it to another editor to make the call on reverting.--JohnBlackburne^words_deeds 01:23, 17 March 2012 (UTC)

Yeah, it looks bad. Unlike any redirect, soft or hard, I have encountered. But otherwise I agree with the rest of David's points. Δρ.Κ. ^{λόγοςπράξις} 01:52, 17 March 2012 (UTC)

I like it and it serves a purpose for this common misconception. Now people need to find this misspelling in current wikipedia articles and correct them. A fine example of the point. — Preceding unsigned comment added by 99.236.135.28 (talk) 01:56, 17 March 2012 (UTC)

From this link to "centrifical", it would appear there aren't any misspellings, but "mispelling" still has a few. Mild Bill Hiccup (talk) 17:24, 18 March 2012 (UTC)

Well I guess thanks are in order. I can't believe I repeated misspelled that word?? I got in lots of trouble from my grade teacher Miss Pelling about that, too! Now your link takes me to several misspelings of the same word throughout WP 99.251.114.120 (talk) 18:43, 3 April 2012 (UTC)

Not a spelling error

Centrifical force is not a spelling error or a typo in which a letter is omitted or two letters interchanged it is a very common malapropism, or what has informally become known as an eggcorn see also. The word is described not as a typo or misspelling but as 'questionable' English by this source. Rightly or wrongly, the word is in commercial and technical usage. We cannot just pretend it does not exist or that it is just a typo. Martin Hogbin (talk) 10:28, 18 March 2012 (UTC)

I think it's possibly just the result of some people writing it the way they pronounce it, somewhat like "nucular" for "nuclear". Mild Bill Hiccup (talk) 17:24, 18 March 2012 (UTC)

That is exactly what an eggcorn is. The point is that is is in very common usage and we should therefore include it here. Martin Hogbin (talk)

From the citation you provided above: quote: A question came up in the World Wide Words newsletter this weekend about the fictitious word “centrifical”. Would I be right to consider this an example of an “eggcorn”?—–Maybe yes, maybe no. How is this a certified eggcorn then? No talk in the citation about malapropism either. Yet in your edit at the redirect you called it both without a valid citation. Δρ.Κ. ^{λόγοςπράξις} 22:28, 18 March 2012 (UTC)

What would you call it then? It is certainly not just a typo or a spelling mistake, it is not a misnomer, it is a word, generally considered to be incorrect, that seems to be based on a careless pronunciation of 'centrifugal'. Perhaps there is no exact term for this. I think eggcorn is probably the closest but I agree that generally that is based on real words. I am happy to discuss the best way of describing what 'centrifical' is but typo or plain misspelling is certainly wrong. I think the best place to continue that discussion is on the redirect talk page.

More important is the need to include the word here. You will see that 'centrifical' is used as a real word by many sources, that makes it a de facto real word, even if it is considered to be incorrect by many. The redirect works for people who search for 'centrifical' but it does not inform people who read this page only that they might find another word used for the subject. I can see no reason why we should not include it, we have reliable sources stating that it is a alternative (or whatever) word for 'centrifugal' and it is clearly in widespread use. Martin Hogbin (talk) 23:27, 18 March 2012 (UTC)

I am not an expert on linguistics but even apparent experts can't agree on precisely what category to fit it in. If this word can't be categorised, the default is the status quo characterisation, which is a "misspelling". However the frequency of use and the geographic spread of this misspelling, imo, are not great enough, or attested enough by reliable sources, to warrant mention in the article. Δρ.Κ. ^{λόγοςπράξις} 02:08, 19 March 2012 (UTC)

Martin's insistence that "centrifical force" is not a misspelling seems to be based on the misconceptions that misspellings and eggcorns are mutually exclusive categories, and that the classification of a word as "questionable" in the eggcorn database can be taken as referring to its spelling . Hopefully, the eggcorn database's entry on eggcorn itself should be sufficient to dispel the first of these misconceptions. Here is an extract from that entry (emphasis mine):

"Eggcorn_, at first _egg corn_, is the original eggcorn. This misspelling for _acorn_ ..."

As, to the second, it's clear from a half-hour or so's perusal of the entries listed as "questionable" in the database, that that classification refers not at all to the spelling of the word, but to the status of its eggcorniness. Here, for example is an extract from the entry on offened:

"Marked questionable, since it’s unclear whether this is categorizable as an eggcorn."

To qualify as an eggcorn, an incorrectly used word has to have arisen from something more than just a spell-as-you-speak error—even if this is a result of a faulty pronunciation or a mishearing of a correct pronunciation. There has to be some misunderstanding on the part of the eggcorn's user about the meaning, etymology, derivation, or some linguistic feature of the misunderstood word other than merely the phonemes that make up its pronunciation or the letters used to represent those phonemes in writing. In the case of "centrifical", Arnold Zwicky, the author of the entry, seems to think it might qualify as an eggcorn because users might have thought its formation was somehow analogous to those of "Pontifical" from "Pontiff", "typical" from type, "cervical" from "cervix" etc.. Be that as it may, the reference given on the redirect page seems to me to be clearly correct in classifying "centrifical" as a misspelling. In every instance of the use of the spelling "centrifical force" that I have seen, there has been no indication whatever that the user of the term meant it to refer to anything other than what the vast majority of other people are referring to when they use the term "centrifugal force", and this latter spelling of the term is the only one recorded in all mainstream dictionaries I have consulted, including the OED.

David Wilson (talk · cont) 04:14, 19 March 2012 (UTC)

Very well said. Rracecarr (talk) 23:11, 19 March 2012 (UTC)

A degree of common sense is required here. A misspelling is when a person wishes to write a particular word but spells it wrongly. That is clearly not the case with 'centrifical'. It is quite obvious that the many sources that use this word were not intending to write the word 'centrifugal' but did not know how to spell it. These sources clearly believe that there is a word 'centrifical'. Whether it is a real word, a misnomer, and eggcorn, or a malapropism, is unimportant. It is clearly not a typo (when someone intends to write one thing but actually writes another) or a misspelling (when someone intends to write a particular word but spells it wrongly). It is also quite obviously in common use to mean centrifugal and it is a cause of possible confusion amongst readers. We have the opportunity to help and inform our readers about correct terminology. Why do we not do that? Martin Hogbin (talk) 09:58, 19 March 2012 (UTC)

A spelling error is still a spelling error if it is frequently made. It would not be wise to give it more weight by including it in the article. −Woodstone (talk) 16:41, 19 March 2012 (UTC)

It is not a spelling error it is a different word. Martin Hogbin (talk) 20:53, 19 March 2012 (UTC)

I guess I will leave you chaps to it. You seem more interested in making some point about the exact status of 'centrifical' than helping our readers. Martin Hogbin (talk) 19:24, 20 March 2012 (UTC)

Why indeed don't we forget about this centrificial business? After all, wouldn't centrifictitious be much more appropriate? Sorry, couldn't resist :-) - DVdm (talk) 19:34, 20 March 2012 (UTC)

'Centrinertial' would be better. Martin Hogbin (talk) 22:52, 20 March 2012 (UTC)

A simple google.ca search nets 130,000 results including education texts & videos and dictionary entries for the term "centrifical force". 99.251.114.120 (talk) 02:41, 28 March 2012 (UTC)

To quote a further example: On the International Space Station in the video "Dan Burbank Gives a Station Tour" (April 2011) he distinctly uses the term "centrifically" in the video broadcast from the ISS, on two occasions. It is definitely a problem with the term being taught with the incorrect spelling. 99.251.114.120 (talk) 13:14, 23 April 2012 (UTC)

If you listen carefully, I believe you will find that the third vowel in Burbank's pronunciation of the word is neither the close front /i/, nor the near-close near-front /ɪ/, but the indeterminate vowel sound known as a "schwa", and represented by the symbol ə. It's difficult to determine by ear whether the consonant which follows that vowel is the unvoiced velar plosive /k/ or the voiced one /g/. To me, it sounds more like the latter on the first occasion when he uses the word, but more like the former on the second occasion. Nevertheless, since the standard pronunciation uses the voiced version of the consonant, I would assume that that's what Burbank was using on both occasions, and the combined sensitivities of the recording and my ears were simply insufficient to detect it on the second occasion. His pronunciation on the first occasion sounds to me like what would be expressed as /sɛnˈtrɪfəɡliː/ in the International phonetic alphabet, and on the second occasion by what would be expressed as /sɛnˈtrɪfəkəliː/, both of which are pretty close to a standard US pronunciation of the word "centrifugally", as recorded in the Merriam-Webster on-line dictionary. I believe this latter would be expressed as /sɛnˈtrɪfjəɡəliː/ in the International phonetic alphabet. The only differences in Burbank's pronunciations is that he doesn't iotise the third syllable, he appears to have essentially omitted the second-last syllable entirely on the first occasion he pronounces the word, and appears to have voiced the velar plosive only very weakly on the second occasion. However, it may well be that the last two of these are only apparent differences resulting from the inadequate sensitivity of the recording and my hearing.

In short, I don't believe there's anything at all in Burbank's pronunciations to suggest that he would spell the word "centrifically". On the contrary, since his pronunciation is barely distinguishable from a standard way of pronouncing the word "centrifugally" I expect that that's the way he would spell it.

David Wilson (talk · cont) 16:51, 23 April 2012 (UTC)

What about the 130,000 results including education texts & videos and dictionary entries for the term "centrifical force"? Martin Hogbin (talk) 22:27, 23 April 2012 (UTC)

What about them? 130,000 google page hits is a trifling number for a misspelled word. For the really common misspellings "miniscule" and "concensus" I get 9,320,000 and 7,440,000 google page hits respectively, as opposed to only 168,000 for "centrifical". Even for "derivitive" I get 1,650,000. However, these raw numbers don't really mean very much, since they're obviously going to be strongly correlated with the frequency of the words they're misspellings of. A somewhat more meaningful comparison might be obtained by taking ratios of the page hits for the erroneous spelling to those for the correct spelling. For the correct spellings "centrifugal", "minuscule", "consensus" and "derivative" I got 4,670,000, 14,400,000, 104,000,000 and 21,500,000 page hits respectively, giving values of 0.036, 0.65, 0.072 and 0.077 for the ratios "centrifical"/"centrifugal", "miniscule"/"minuscule", "concensus"/"consensus" and "derivitive"/"derivative". I wouldn't place much reliance on google page hits as a tool for drawing lexicographical conclusions in any case, but there's certainly nothing I can see in these figures to indicate that the misspelling "centrifical" for "centrifugal" is any more remarkable than "derivitive" for "derivative".

I would also point out that by the measure of google page hits "centrifical" isn't even the most common misspelling of "centrifugal". For "centrifigal" I get 558,000 hits, more than three times as many as for "centrifical". Admittedly, a large majority of these will be simple typographical errors in which the "i" key on the keyboard has been mistakenly struck in place of the adjacent "u" key, but there are also certainly a large number of them which are obviously not of this type. It seems pretty obvious to me that the occurrences of "centrifical" and "centrifigal" that are genuine spelling errors—as opposed to simple typos—must be ultimately traceable to a spell-as-you-hear mistake, so I would expect them to be roughly equally frequent.

David Wilson (talk · cont) 14:17, 24 April 2012 (UTC)

Try "centrifical force" vs "centrifigal force". The point is that there are people who believe that the correct term is 'centrifical' and who consistently spell it and pronounce it that way. The same is not true for other misspellings of the word.

I really cannot see the objection to educating our readers with a short phrase along the lines of, 'sometimes erroneously called centrifical...'. Looking at the Google results it is clear that many people are utterly confused by the subject, an encyclopedia should enlighten them. Martin Hogbin (talk) 17:44, 24 April 2012 (UTC)

"Try "centrifical force" vs "centrifigal force"."

I get 31,800 page hits for the former, and 7,520 for the latter. What particular significance did you wish to attach to these figures?

" The same is not true for other misspellings of the word."

Really? And you know this how, precisely? When someone writes "centrifucal" four times, including once after someone else in the discussion has spelt "centrifugal" correctly, why would you presume that he doesn't misspell it that way consistently? And why would you presume that he would pronounce it any more correctly than someone who writes it "centrifical"?

"I really cannot see the objection to educating our readers with a short phrase along the lines of, 'sometimes erroneously called centrifical...'"

Just because you cannot see an objection doesn't mean that there isn't any. Readers who already know how to spell correctly, and arrive at the article by typing its title correctly—or by searching on the correctly spelt term "centrifugal force"—, don't need, and most likely don't particularly want, to be informed that some people incorrectly write it as "centrifical force", any more than if they were reading the article Derivative they would want to be informed that some people misspell that term "derivitive". I know that I personally find such gratuitous asides a distracting annoyance whenever I come across them.

I see that Dick Lyon has just recently reverted the soft redirect at Centrifical force back to a hard redirect with the (erroneous, in my opinion) edit summary "no justification for not using a hard redirect here". The problem with the hard redirect is that readers looking for an article on Centrifical force simply land at the article Centrifugal force with only a very inconspicuous message "(Redirected from Centrifical force)" under the main heading to indicate why they've arrived at the latter article rather than the former one they had actually been looking for. Ideally, that message should be much more conspicuous, and say something like "There is no English word which is correctly spelt "centrifical", although the word "centrifugal" is sometimes misspelt that way. Did you mean Centrifugal force?". However, there seems to be no way of getting such a message to appear after a hard redirect without changing the MediaWiki software. In the absence of such a capability, putting some similar message on a soft redirect seems to me to be much more useful service to our readers than inflicting the uninformative hard redirect on them

David Wilson (talk · cont) 03:35, 25 April 2012 (UTC)

You still seem to think that 'centrifical' is just a misspelling of 'centrifugal'; it is not. It is a different word; one that does not exist in correct English but one that has its own consistently used spelling and pronunciation.

I understand the need to reduce distracting clutter in an article but we have had at least one user who was puzzled that the term 'centrifical force' was not mentioned at all in WP. WP is not just for people who already know the answer to confirm their knowledge, it is also for people with vague or incorrect notions on a subject. We need to help their understanding and put them back on the right track. Martin Hogbin (talk)

I would point out that the only reliable source anyone has so far provided as making any pronouncement on the lexicographical status of "centrifical" lists it as a misspelling of "centrifugal" in a list of "frequently misspelled words". This seems obviously correct to me, and I simply do not accept that "centrifical" should be classified as a different word from "centrifugal", rather than simply a misspelling of it. As far as I can see you have provided no cogent reason why I should change my mind. I would be prepared to wager that if mainstream dictionaries ever get around to including "centrifical" (with pronunciation /sɛnˈtrɪfəkəl/ or /sɛnˈtrɪfɪkəl/ ) in their publications, it will be as an alternative spelling and pronunciation of "centrifugal" and not as a separate word.

David Wilson (talk · cont) 13:09, 25 April 2012 (UTC)

I see no point in arguing about the precise lexicographical status of 'centrifical'. I am not sure whether it is a malapropism, an eggcorn or something else. Clearly it is a corruption in both spelling and pronunciation of 'centrifugal' but many people seem to think that it is a real word. We have the opportunity to explain that it is not and that the correct word is 'centrifugal' thus replacing ignorance with knowledge. That, I though, was one of the main purposes of WP. Martin Hogbin (talk) 14:30, 25 April 2012 (UTC)

I'm perfectly happy to drop the issue of the precise lexicographical status of "centrifical".

As for replacing ignorance with knowledge, there will always be a limit to the extent to which we can do this for the more poorly informed of our readers without treating the better informed of them as nincompoops. In my opinion it's generally inadvisable for writers of articles not specifically devoted to grammar or spelling to presume that their readers' knowledge those subjects is any worse than their own. To tell readers of such articles that such-and-such a spelling or word usage is a common error carries the uncharitable insinuation that those readers are incapable of recognising this for themselves without the writer's assistance, or worse, that they're suspected of belonging to the despised horde of ignoramuses who might well be capable of perpetrating such a blunder.

In the case of "centrifical force", I would not take it upon myself to presume that a typical reader of the article is any less capable than you or I of recognising that it's an erroneously spelt reference to the same concept which they know of as "centrifugal force". For such of those readers who have so far remained blissfully ignorant of the lamentably common occurrence of this error, I don't believe it should be any part of the article's role to hasten the sorry day when they're made aware of that fact.

As for correcting the misunderstandings of those readers of the article who have habitually referred to its subject as "centrifical force", it should be sufficient for the article merely to use the correct terminology. And in conjunction with the hard redirect from Centrifical force, this was in fact sufficient for the original poster to this thread to realise that "centrifical force" was an error. Personally, I think it would be more useful for these readers—and would do no harm at all that I can see—for the current hard redirect to be replaced with the soft redirect that Dicklyon recently changed back to the former. But it's not really an issue that I can get all that worked up about.
David Wilson (talk · cont) 15:27, 27 April 2012 (UTC)

I guess we could leave our readers to work most things out for themselves rather than insulting their intelligence by explaining things to them but this is meant to be an encyclopedia and if one short sentence can put misinformed readers straight that seems good value to me. Martin Hogbin (talk) 08:39, 30 April 2012 (UTC)

I'll have to leave you guys to it. The OCD crowd has reared it's ugly head and insist on not clarifying the nonsense. IPs have no rights to take matters to a higher authority for arbitration or other methods and I am tired of the threats made upon myself for any attempts to persist to clarify the magic redirect. Thanks. 99.251.114.120 (talk) 02:13, 30 April 2012 (UTC)

Why do you not register then? It is not that hard and there is no downside. Martin Hogbin (talk) 08:35, 30 April 2012 (UTC)