Wikipedia:Reference desk/Archives/Miscellaneous/2016 June 27

Welcome to the Wikipedia Miscellaneous Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 27

Stiletto heel vs. tank

How does the pressure under a stiletto heel compare to the pressure under the track of a Sherman tank? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 06:23, 27 June 2016 (UTC)

Very much greater. So much greater, in fact, that we can use the Fermi estimation beloved of xkcd:

• Weight of female : 100 kg = 1000 N
• Area of heel : 1 cm² = 0.0001 m²
• Pressure of heel : F / A = 1,000,000 Pa

• Weight of tank : 100 t = 1,000,000 N
• Area of tracks : 10 m²
• Pressure of tank : F / A = 100,000 Pa

So, about one order of magnitude greater. Tevildo (talk) 08:13, 27 June 2016 (UTC)

Wow! That's incredible! Thanks! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 11:07, 27 June 2016 (UTC)

• I'm pretty sure 100kg (around 220lb) is not the average weight for a woman (or perhaps it is, in the USA). Using UK data, though, it's around 70kg - so the pressure is about 7 times as great, not 10. Laura Jamieson (talk) 11:08, 27 June 2016 (UTC)

• Yes, all the numbers in my calculation are just to the nearest power of 10. More accurate figures can, of course, be used, but this is close enough to give us an answer to the OP's question without having to look things up. Tevildo (talk) 13:17, 27 June 2016 (UTC)

So this Rodney Dangerfield line had some potential truth to it: "This girl I dated was so fat that when she wore high heels she would strike oil!" ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:36, 27 June 2016 (UTC)

1000 / 0.0001 is actually 10,000,000 (not the 1,000,000 you put in) - which makes it 2 orders of magnitude greater. For the record - the average weight of a British woman is approximately 70 kg, while a Sherman tank weighed about 30 tonnes. That makes the pressure from the stiletto a bit more than 200 times that of the tank. All this shows is that tank tracks work - they spread the weight of a massive vehicle so that it doesn't sink into the ground. Wymspen (talk) 14:11, 27 June 2016 (UTC)

This article on the 62,500 kg Challenger 2 Main Battle Tank, quotes a ground pressure of 0.9kg/sq.cm. Not sure how that converts into Pascals though. Alansplodge (talk) 20:32, 27 June 2016 (UTC)

I'm not sure Pascal is a good unit for this (although formally it works). A Pascal is a Newton per square meter. 0.9 kg exert a force of about 10 Newton. One square meter has 10000 square centimetres. So 0.9 kg per square cm is 100000 Newtons per square meter, or 1000 hectopascal. It also fits well with the two orders of magnitude compared to a somewhat heavy women on stilettos (or rather "with her full weight on one stiletto", which sounds rather acrobatic to me). --Stephan Schulz (talk) 21:27, 27 June 2016 (UTC)

Hmmm - I don't like 10m² as the ground-contact area of the tank's tracks - the entire underbelly of the tank is only about that much. That seems awfully high - and gives the stiletto a huge advantage! The tricky part of this is that tank tracks have flat plates with protruding ridges. The contact area of the ridges alone on a hard surface would be far less than even 1m² - but on a soft surface, those would dig into the ground and the large flat area of the track would be in contact with the ground - vastly increasing the contact area (although not, in my estimation, as much as 10m²). In peacetime, tanks are often fitted with large rubber pads that increase the contact area even on hard surfaces in order that they can drive on asphalt roads without tearing them up unduly. I think without those pads - and on a hard surface - the tank might give the stilettos a run for their money...but a lot starts to depend on the nature of that surface and precisely which tank (and which woman and which stilettos) are being discussed. I think the fermi estimation stops being a convincing tie breaker at that point and we have to resort to a more concise description of the situation and some more precise calculations. Right now, I'd say it's a wash. SteveBaker (talk) 22:07, 27 June 2016 (UTC)

Now that I come to think about it - we're also making a mistake in presuming that the weight of the tank is equally distributed over the entire area of the track. That's really not true. The track is flexible and the road wheels of the tank don't apply their weight evenly on every individual tread. The tracks aren't under a LOT of tension - so I would not be surprised to learn that the pressure on each tread would change by quite a large factor as each road wheel in turn rolls over it. As with my previous comment - a lot depends on how soft the ground is. If it's very soft then the treads that are under more pressure will sink a little - allowing more weight to be distributed onto the adjacent treads - but on a hard surface, that's not going to happen...so gut feel says that I could easily believe that the peak downforce at a particular point along the track would vary by maybe a factor of two as the tank rolls over them on hard ground - but be evenly spread on soft ground. This again erodes the lead gained by the stilettos.

But then, who can balance on one or even two stiletto heels? When someone walks on them, the weight should surely be almost entirely on the ball of the foot - not the heel. When walking in such shoes, it is not the heel that strikes the ground first (I think). The wearer is more or less walking on the balls of their feet with the heel acting only as a prop when they stand still. Only when the wearer stops walking would any significant fraction of the weight be on the heel...but the steep slope of the smooth insole of the shoe must result in much of that weight being transferred forwards...for any degree of comfort, the sole is unlikely to be horizontal over the heel area. SteveBaker (talk) 22:24, 27 June 2016 (UTC)

In this video: https://www.youtube.com/watch?v=BgiAIv12TPs and this one https://www.youtube.com/watch?v=VZry9dEOqGk it's really clear that at no point does the heel bear all of the woman's weight...and the sole has a vastly larger area than the heel. Now I'm starting to believe that this idea is very, very busted! There is no way that a person who isn't trying very hard to destroy their shoes can apply more pressure than a tank on a hard surface...and on a soft surface where the tank is designed to spread it's weight over a larger contact area, it's entirely moot because this kind of footwear is a disaster in soft ground.

This is a classic example of where a naive calculation - without careful observation - produces an astounding (and almost certainly incorrect) result. SteveBaker (talk) 22:33, 27 June 2016 (UTC)

Let's have some sources, shall we? This site gives the ground pressure of the tank as 0.962 kg/cm², or 96.2 kPa 94.3 kPa. This site (less authoritative, admittedly, but the numbers all seem reasonable) gives numbers for the pressure of stiletto heels between 1700 kPa and 11,000 kPa. The crude calculation for the tank turns out to be about right, and that for the heels towards the upper limit of reasonable values, but, even using the lowest value for the heels, they still exert 17 times more pressure than the tank. The tank may do more damage to most surfaces, but that wasn't the question. Tevildo (talk) 23:21, 27 June 2016 (UTC)

Updated number in the above posting - I didn't convert kgf to newtons properly. Tevildo (talk) 00:22, 28 June 2016 (UTC)

Lets examine your sources a little.

The trouble with the high-heels numbers you found is that they are all theoretical numbers that assume that the entire weight of the wearer is pressing down hard on one heel for some part of the stride - which is simply not what happens when people walk or stand in them. Just look at the structure of the shoe and that becomes readily apparent. In videos of women walking in these shoes, it's VERY obvious that heel and toe hit the ground at the same time. Even if the heel did happen to hit the ground a tiny fraction of a second before the toe, the person's weight will not be fully on that foot at the time. By the time the other foot is lifted, the weight is planted on the front part of the shoe - which has a much larger surface area - and the slope of the insole at the heel of the shoe (which looks to be between 45 and 60 degrees in the photo I posted above) will result in a forward thrust that pushes the wearer to apply more weight onto the front part. The exception to that MIGHT be if people run in the shoes because when running, there is only one foot on the ground at a time - but you can't run in high heels without either running on the front section of your foot or clonking along flat-footedly. Truly running in heels only happens in the movies - and 100% of the time, the heel breaks off and our heroine is running barefoot from that point on!

The tank numbers you have seem more reasonable - but I still suspect they are computing an average pressure over the entire track and not just at the point where the road wheels are applying pressure the most...which is presumably what we care about here.

So let's look at the M4 Sherman that you mentioned (picture at right). It weighs 30,300 kg and it's 5.8 meters long. The tracks look like they are in contact with the ground over perhaps 5 meters. The width of the tank is 2.6 meters - and the tank tracks are clearly less than 1/5th of that width because someone has helpfully laid five of them out over the front. So each track is about 0.5m x 5m which is 2.5m² each - 5m² together. Now - look at the tank treads carefully - they have that U-shaped protruding surface. If that surface is pressed into some soft dirt - then we have 30,000kg spread over 5m² which is 0.6kg/cm² That's less than the 0.962kg/cm² that your source quotes...so probably either I've over-estimated the width of the tracks somewhat or 30,000kg is the unladen weight and the 0.962kg/cm² number is for a tank full of ammo, fuel, etc. But when you look at the protruding U-shaped surface on each tread - that's gotta be no more than a quarter of the area of the tread itself...that suggests that the pressure on the contact area on a hard surface is four times higher than on a soft one. There is no possible way that the 0.962 kg/cm² number can possibly be correct for a tank that's resting on those thin shiny sections. So the number quoted MUST be on the basis of the entire width of the tread being in contact with the ground and sharing the load...which is great for somewhat soft surfaces that allow the protruding part of the tread to bury itself into the ground a little - or if they have rubber blocks bolted to the tracks as is commonly the case in peacetime. I conclude that the pressure on a firm surface of a tank without the load-spreading block is probably three to four times higher than quoted...mathematically, it just has to be...sources be damned!!

Now take a look at the road wheels of the M4 - there are six on each side. How many tank treads are actually being pressed into the ground by those wheels? Well - it certainly appears from the photo that each wheel is fully resting on only one or two links of the track at a time...how could it be otherwise when a steel wheel is resting on a solidly supported track? So of the 26 or so links that touch the ground, only at most 12 of them are sharing the weight. You can see from the upper section of the track that it hangs a little loose across the idler wheels at the top - so there isn't much tension in the thing - the amount of weight that would be transferred from one link to the next by their loose horizontal connection just isn't that great. So that suggests that the ground force is at least twice the estimate you get from dividing the weight of the tank by the area of the track that's on the ground.

The M4 Sherman is a pretty lightweight tank...thin skimpy armor. Take the Sherman's German contemporary, the Tiger tank - it's almost twice the weight, about the same length - and the tracks look a little wider but not by much - and the treads rest on the ground on a thin horizontal member that's most definitely thinner than the treads on the Sherman, and with only four road wheels on each side - the weight isn't distributed over as many links. What constitutes a "typical" tank? I don't know - but picking the Sherman is cherry-picking one of the lighter ones!

On that basis, I'd say that the ground pressure of the Sherman on an unyielding surface is perhaps six to eight times what is quoted in your source - and that of a Tiger, more like ten to fifteen times. That's not as much as the naive calculations for the stiletto - but it's simply not credible that the wearer of such shoes could ever put their entire weight over one heel. No! Not anatomically possible! Perhaps, with some determination, a person could place half their weight on one heel...but with a factor of 17 between tank and heels using the numbers from your sources - my claim that the tank numbers are too low by a factor of 6 to 8 and the heel numbers are too high by at least a factor of 2 - means that we have a dead heat...but that's only when the surfaces they're standing on are hard and the shoe wearer is determined enough! I don't buy that! The tank wins - albeit narrowly!

SteveBaker (talk) 01:18, 28 June 2016 (UTC)

"It just has to be...sources be damned!!" I make no further comment. Tevildo (talk) 12:32, 28 June 2016 (UTC)

Taking sources at face value - without examining their applicability, premises and assumptions - is a disastrous way to find the truth.

The math used in the source you provide for the stiletto numbers clearly calculates the entire weight of a person balancing on one heel. I don't dispute that the numbers they arrive at would be correct if someone actually did that - but that's not a reasonable (or even anatomically possible) situation! That source is a great source for what would happen if someone could do that - but it's no source at all for the actual pressure of an actual stiletto shoe in an actual situation...so it's utterly irrelevant here. Similarly with the number quoted for the pressure of the tank track - you can do the arithmetic yourself and deduce that whoever wrote that book took the weight of the tank and divided it by the length and width of the track without considering the pattern of the tread or the unevenness of the road wheels when applied to an unyielding surface. Just because someone wrote that number down in a book without clarifying exactly what they mean by that doesn't make it applicable here. So I stand by my conclusion. SteveBaker (talk) 17:16, 28 June 2016 (UTC)

But you need to check your assumptions both ways. The normal use case for a stiletto is to be walked in (a dynamic process) on a hard surface. Also, http://www.whowhatwear.co.uk/how-to-walk-in-heels suggests keeping your weight back and touching the heel to the ground first. So it's not implausible that your whole weight is on the heel for at least part of a stride (and maybe even more if you accelerate or decelerate). On the other hand, the normal use case for a tank is to drive on a soft(er) surface, and with a process that usually has less of a vertical component than walking. Moreover, the tank will most likely deform the surface until the pressure is largely equalised over the contact surface, and will "only" press down with its weight, not a large dynamic component (unless it jumps obstacles ;-). --Stephan Schulz (talk) 10:33, 29 June 2016 (UTC)

How to run a edit-a-thon on WP ?

How to run a edit-a-thon on WP ? I have checked the article, but can't it be online? — Preceding unsigned comment added by Aryan hindustan (talk • contribs) 06:32, 27 June 2016 (UTC)

Can you make your question a bit clearer, Aryan hindustan? WP:EDITATHON specifically says "whether offline, online, or a mix of both". What is it you're having difficulty with? --ColinFine (talk) 10:49, 27 June 2016 (UTC)

Is the OECD, a "genetically" Euro-pacific organization?

Every OECD member turns out to belong, either to the Apec (the organization of countries bordering the Pacific Ocean), or to the Council of Europe (with only one OECD member as an exception). Furthermore, all four current candidates which are about to join the OECD soon, are Euro-pacific as well. Really, from a formal viewpoint - being a Euro-pacific country - has never been put as a condition for being an OECD member, but from a practical point of view - the facts are unambiguous. I wonder, if the OECD has something in its "genes", that makes it have such a salient "Pacifico-European" orientation. HOTmag (talk) 18:36, 27 June 2016 (UTC)

The OECD is, by definition, an organisation for developed countries with democratic systems of government. Those just happen to be in the areas you have identified - but that has more to do with history than with geography. Wymspen (talk) 20:17, 27 June 2016 (UTC)

This is exactly what I'm asking about:

Historically, why have all "developed countries with democratic systems of government" (as you define them), become a part of the Euro-pacific area? HOTmag (talk) 20:42, 27 June 2016 (UTC)

I think that's the wrong way round. It's like asking why France became part of Europe. I think you're really asking "Historically, why is it that only countries in the Euro-pacific area have become "developed countries with democratic systems of government" (as you define them)". -- Jack of Oz ^{[pleasantries]} 22:35, 27 June 2016 (UTC)

Thank you Jack, for the clarification of what I meant. HOTmag (talk) 23:29, 27 June 2016 (UTC)

Well, it is true that originally the OECD was the Organisation for European Economic Co-operation, founded to help implement the Marshall Plan, and its original membership was limited to Europe and North America. --71.110.8.102 (talk) 23:02, 27 June 2016 (UTC)

But also when the OECD was enlarged and even doubled, it was still limited to the Euro-Pacific area... HOTmag (talk) 23:29, 27 June 2016 (UTC)

NO. It was limited to countries which met its membership criteria. It is just a historical fact that those countries happened to be in certain areas. The fact that Japan, South Korea and Chile are now members rather shows that the organisation is happy to extend to other parts of the world if the basic criteria are met. Wymspen (talk) 14:30, 28 June 2016 (UTC)

Not only the three countries you've mentioned. Please notice that not less than thirteen countries joined the OECD since its establishment in 1961 (regardless of Italy that joined the OECD half a year later but had already belonged to the previous organization: OEEC), and all of them are in the Euro-Pacific area, as following: Seven new members were taken from Europe: Czech Republic, Estonia, Finland, Hungary, Poland, Slovakia, and Slovenia; Whereas six new members were taken from APEC (the organization of countries bordering the Pacific Ocean): Australia, Chile, Japan, Mexico, New Zealand, and South Korea. Furthermore, all four current candidates which are about to join the OECD soon, are Euro-pacific as well. HOTmag (talk) 15:14, 28 June 2016 (UTC)

Japan, Australia and New Zealand were members of the OECD before APEC was even founded - so their membership is in no way linked to their being part of APEC. And you continue to miss the key point - membership of the OECD is NOT limited to countries from the "Euro-Pacific" area: it is limited to countries with a certain form of economy and government. Countries from other geographical areas who met the membership criteria could apply to join on the same terms. Brazil, India, South Africa and Kazakhstan are all in some sort of arrangement or negotiation at the moment. Wymspen (talk) 13:16, 29 June 2016 (UTC)

• "You continue to miss the key point - membership of the OECD is NOT limited to countries from the "Euro-Pacific" area ". It seems like you miss my point, while repeating what I have already written in my first post, so let me quote myself: "Really, from a formal viewpoint - being a Euro-pacific country - has never been put as a condition for being an OECD member". Further, it seems like you've missed the rest of that sentence, so let me quote it: "but from a practical point of view - the facts are unambiguous".
• "Japan, Australia and New Zealand were members of the OECD before APEC was even founded - so their membership is in no way linked to their being part of APEC ". It seems like you miss my point. The APEC is not the point. The point is, countries located in Europe or bordering the Pacific Ocean. That's why I've called it: "the Euro-Pacific area". The Apec is only the political frame of those countries (so that every APEC member must border the Pacific Ocean). Anyways, The facts are unambiguous: Every OECD member, whether a founding member or a joining member, is located in the Euro-Pacific area.
• "Countries from other geographical areas who met the membership criteria could apply to join on the same terms ". Could apply, and many of them have really applied, but the fact is unambiguous: None of them have been invited to join, so far.
• "Brazil, India, South Africa and Kazakhstan are all in some sort of arrangement or negotiation at the moment ". None of those countries is in accession negotiations. HOTmag (talk) 15:37, 29 June 2016 (UTC)

When did Israel (an OECD member since 2004) become a Euro-Pacific country?DOR (HK) (talk) 10:15, 29 June 2016 (UTC)

In two hugely important ways, since 1973 and 1992/1994. More seriously, Israel has membership of lots of European bodies. --Dweller (talk) Become old fashioned! 10:23, 29 June 2016 (UTC)

It seems like you haven't read the small letters in my first post, so let me quote myself: "Every OECD member turns out to belong, either to the Apec (the organization of countries bordering the Pacific Ocean), or to the Council of Europe (with only one OECD member as an exception)". HOTmag (talk) 15:37, 29 June 2016 (UTC)

So you ask if there is something in the "genes" - which to me means the rules, regulations, constitution, charter or whatever. To which I repeatedly have answered that there is not - and that the geographical spread is just a matter of history and economics. What else are you trying to ask? Wymspen (talk) 16:02, 29 June 2016 (UTC)

By "genes" I didn't mean anything legal or regulatory. Just as, English has something Indo-European in its "genes", although nothing in its grammar prevents it from borrowing words from Chinese or from Arabic. HOTmag (talk) 16:31, 29 June 2016 (UTC)

Genes, in the literal, scientific sense, are the set of codes which determine what form an organism takes. The things which determine the form an organisation takes are its legal documents - charter, treaty, constitution, articles, rules, or whatever. I don't understand your linguistic analogy - I can't see that genes applies in any way to the evolution of a language or its grammar. Wymspen (talk) 16:43, 29 June 2016 (UTC)

"I can't see that genes applies in any way to the evolution of a language or its grammar ". See our article: Genetic relationship (linguistics). For example, English, is considered to have "genetic" connections with German and Dutch, just as Russian is considered to have "genetic" connections with Polish and Czech. HOTmag (talk) 16:59, 29 June 2016 (UTC)

Disappearance of a chart in a WP article

How do I find the linear chart that was present this morning in the Wikipedia article "Nationwide opinion polling for the United States presidential election, 2016"? It is no longer there this afternoon. It was removed sometime today, and was the only one I was able to find anywhere that clearly showed Sanders vs Trump and Clinton vs Trump from Jan 1st to June 1st on all the 83 nationwide polls. Where is it, and why was it removed? I take strong issue with removing it unless it was found to be bogus. 1originalee (talk) 19:57, 27 June 2016 (UTC)

Someone deleted it - someone else put it back - it may have been vandalism (someone doesn't like the results), or it may genuinely have been a belief that the information was no longer relevant. The person who did it is anonymous, so there is no way to know. It all seems to be there now. Wymspen (talk) 20:13, 27 June 2016 (UTC)

Here is a link to the article: Nationwide opinion polling for the United States presidential election, 2016. When something disappears from an article, use the "View history" tab to see who edited it - and what they did. In this case, you can see that an anonymous user (User:107.182.201.26) deleted 168,000 characters from the article - but it was replaced by "ClueBot" within a minute or so. Then User:Mmulroney removed that chart - saying: "‎Individual polls: Chart very out of date, not informative about the current state of the race. I guess someone lost interest once pollsters stopped asking Bernie vs Trump.". I'm not sure whether that was a valid thing to do - Wikipedia is an encyclopedia, not a news outlet - so outdated information may still be important in the future. Anyway, looking at what Mmulroney deleted - you can see that the chart is still here:

SteveBaker (talk) 21:53, 27 June 2016 (UTC)

I removed the chart because it wasn't being updated, and as a result, didn't really belong on a page showing the current state of the race between presumptive nominees. When you look at a chart, you need to ask "what does this or is this intended to convey, and is it relevant?" The chart conveyed "Sanders does better than Hillary against Trump up to 3 weeks ago when pollsters stopped asking." On a page intended to show the current state of the race, it was a distraction - people are better off sifting through more recent polls than looking at an outdated chart.

I had no intention of vandalizing or destroying information. If I had time to update the chart, I would have and would have kept Sanders' on the chart as long as he hadn't conceded (although his line would have stopped in early June as most pollsters stopped asking). But if a chart isn't updated for several weeks when new data is released almost daily, it needs to be removed, lest people visiting the site rely on the graph for current information. Mmulroney (talk) 15:06, 29 June 2016 (UTC)

But as Steve said, this is supposed to be an encyclopedia, not a news outlet. Generally, information shouldn't be added to an article unless it will continue to be relevant after the situation changes. It's not clear to me that it's appropriate for this article to exist at all, but if it is, then showing data from old polls is appropriate too. Anyway, if thi sis going to be debated it would be better on the article's talk page. --69.159.60.163 (talk) 17:50, 29 June 2016 (UTC)

I'm not sure you understand the issue or what is being discussed. Polling data is absolutely relevant and will continue to be relevant after the election, as the predictive validity of polls and their relation to certain events are important topics for political scientists, statisticians etc. For posterity, there is also value in showing all of the theoretical matchups between withdrawn/mathematically eliminated candidates. Whether Bernie should appear on a chart of current polling is debatable because he is technically still contesting a nomination, yet pollsters are no longer asking about his hypothetical numbers vs Trump. I deleted a chart not because it showed Bernie v Trump matchups, but hadn't been updated since early June. The issue with the graph that I removed wasn't that it contained old polls - it was the lack of new ones. Whoever was updating it apparently stopped doing it when Clinton became the presumptive nominee and pollsters stopped polling Bernie vs Trump. It didn't belong in a section showing current polls. I don't care whether or not there is a chart, but if there is one in the section that includes current polling, the chart needs to be maintained relatively regularly or removed. The reason for my deletion is moot (for the time being) because someone updated it.Mmulroney (talk) 21:40, 29 June 2016 (UTC) User:1originalee, I hope this addresses your concerns. Mmulroney (talk) 00:03, 30 June 2016 (UTC)