User:FreeT/Physics Equations

Please do not edit this page. This is part of FreeT's space to type thoughts to use for a later time, giving a higher quality to the finished article.
This subpage is about physics equations on the Irish Leaving Certificate sylabus. You may of course copy material from here, just please don't edit it. If you can come up with some good mnemonics, please enter them.

*Edit*
From the 2010 Leaving Certificate on, new log tables will be supplied for the exams which will include most of the following formulae. Still, I'll finish the list for anyone who would like to learn them, or needs to learn them for a different exam.

Reflection of Light from Spherical Mirrors

Reflection of light in a spherical convex mirror.

Formula	Abbreviations	Mnemonic
${\frac {1}{u}}+{\frac {1}{v}}={\frac {1}{f}}$	u - distance from the object to the mirror v - distance from the image to the mirror f - focal length nb, v is + for real image v is - for virtual image f is + for concave mirror f is - for convex mirror
$m={\frac {v}{u}}$	m - magnification u - distance from the object to the mirror v - distance from the image to the mirror	over under

Refraction

Refraction in a Perspex (acrylic) block.

Formula	Abbreviations	Mnemonic
${\frac {Sin(i)}{Sin(r)}}=n$	i - Angle of incidence r - Angle of refraction n - Refractive Index between the two media	Being rare gets presidence over being dense
$_{x}n_{y}={\frac {1}{_{y}n_{x}}}$	For any two media x and y n - Refractive index between the two media
$n={\frac {\mbox{Real depth}}{\mbox{Apparent depth}}}$	n - Refractive Index of medium	Real truth presides over apparent truth anyday
$n={\frac {\mbox{Speed of light in vacuum}}{\mbox{Speed of light in medium}}}$	n - Refractive Index of medium	The vacuum is always lighter, so it rises to the top
$n={\frac {1}{Sin(C)}}$	n - Refractive Index C - Critical angle

Lenses

Convex lens in action

Formula	Abbreviations	Mnemonic
${\frac {1}{u}}+{\frac {1}{v}}={\frac {1}{f}}$	u - distance from object to lens v - distance from image to lens f - focal length where: u is always + v is + for a real image v is - for a virtual image f is + for a convex lens f is - for a concave lens
$m={\frac {v}{u}}$	m - magnification v - distance from image to lens u - distance from object to lens
$P={\frac {1}{f}}$	P - power of lens f - focal length	power of lens is measured in per metres
$P=P_{1}+P_{2}$	P - overall power of combination of lenses P1 - power of first lens P2 - power of second lens
${\frac {1}{f}}={\frac {1}{f_{1}}}+{\frac {1}{f_{2}}}$	f - overall focal length of combination of lenses f1 - focal length of first lens f2 - focal length of second lens where: f is given a + for a convex lens and a - for a concave lens.

Temperature

Formula	Abbreviations	Mnemonic
t(C) = t(K) - 273.15	t(C) - temperature in degrees Celsius t(K) - temperature in degrees Kelvin	To serve three-period, single fights. Small number = Big number - a lot.

Quantity of Heat and Heat Transfer

Formula	Abbreviations	Mnemonic
$Q=mc\Delta \Theta$	Q - heat energy m - mass (kg) c - specific heat capacity $\Delta \Theta$ - change in temperature	MCAT
$Q=ml$	Q - heat energy m - mass (kg) l - specific latent heat

Waves and Wave Motion

Surface waves in water

Formula	Abbreviations	Mnemonic
$T={\frac {1}{f}}$	T - time for one cycle to pass a point f - frequency (hz) or cycle per second
$c=f\lambda$	c - velocity of wave f - frequency $\lambda$ - wavelength
$f'={\frac {fc}{c-u}}$	f' - observed frequency f - actual frequency c - speed of wave in the medium u - speed of source nb. u is negative if source is moving away from observer.

Vibrations and Sound

Formula	Abbreviations	Mnemonic
$I={\frac {P}{A}}$	I - sound intensity P - power A - area	Patrick's over-Aim is an Intense miss
$2lf={\sqrt {\frac {T}{\mu }}}$	f - fundamental frequency l - length $\mu$ - mass per unit length T - tension	2 Live freely is the root of tears undue.
$n^{th}$ overtone = $(n+1)^{th}$ harmonic	n - any number
c = 4f (l + 0.3 d)	c - speed of sound in medium f - frequency of note emitted l - length of closed pipe d - diameter of pipe

Static Electricity

Formula	Abbreviations	Mnemonic
$F={\frac {Q_{1}Q_{2}}{4\pi \varepsilon d^{2}}}$	Q1 and Q2 = charges F = force between charges d = distance between charges	Queens over four pies eating a square dinner = very forceful.
$\varepsilon =\varepsilon _{r}\varepsilon _{0}$	E = Permittivity of medium Er = Relative permittivity of medium Eo = Permittivity of a vacuum
$E={\frac {F}{Q}}$	E = Electric Field Strength F = Force Q = Charge	'Free and easy but queasy' triangle

Potential Difference and Capacitance

Formula	Abbreviations	Mnemonic
W = QV	W = Work Done Q = Charge/Number of Coulombs Transferred V = Potential / Voltage	Where is the Queen's Vulture?
$C={\frac {Q}{V}}$	C = Capacitance of a conductor Q = Charge V = Potential / Voltage	'Queens Catch Vultures' Triangle
$Cd=\varepsilon A$	C = Capacitance of a conductor d = Distance between plates E = Permittivity of the dielectric A = Area of overlap of the plates
$W={\frac {1}{2}}CV^{2}$	W = Energy stored in a charged capacitor C = Capacitance of a conductor V = Potential / Voltage nb. This formula gives the average work done It can not be derived by combining W=VQ with Q=VC.	Similar to $W={\frac {1}{2}}mv^{2}$ in log tables.

Current and Charge

Formula	Abbreviations	Mnemonic
Q = It	Q = Charge gone past I = Steady current t = time	Similar to "quit".

Electromotive Force and Potential Difference

Formula	Abbreviations	Mnemonic
W = QV	W = Energy given out Q = Charge gone past V = Potential / Voltage	Where is the Queen's Vulture?
VI=P	V = Potential difference between two points I = Current flowing between two points P = Power dissipated between two points.	Very Important Person

Resistance, Current, Voltage

Formula	Abbreviations	Mnemonic
$R={\frac {V}{I}}$	R = Resistance V = Potential / Voltage I = Current	Ronaldo is Very over Inphasised.
$\rho l=RA$	p = Resistivity of the material in the conductor R = Resistance A = Cross-sectional area l = Length	Pink Light is Readily Accepted
$4\rho l=R\pi d^{2}$	l = Length p = Resistivity of the material d = Diameter of wire R = Resistance	4 Pirate Leaders are Raiding Pies at the square Dance
When a wheatstone bridge is balanced: $R_{1}R_{4}=R_{2}R_{3}$
$P=I^{2}R$	P = Power I = Current R = Resistance	Twinkle, twinkle little star, Power = I squared R
$I_{rms}={\frac {I_{0}}{\sqrt {2}}}$

Series Circuit

Formula	Abbreviations	Mnemonic
$R=R_{1}+R_{2}+R_{3}$	R = Total resistance R1, R2 and R3 are separate resistors in series
$A_{1}=A_{2}=A_{3}$	A1, A2 and A3 are three ammeters in series
$V=V_{1}+V_{2}+V_{3}$	V = Total voltage V1, V2 and V3 are three batteries in series

Parallel Circuit

Formula	Abbreviations	Mnemonic
${\frac {1}{R}}={\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}+{\frac {1}{R_{3}}}$	R = Total resistance R1, R2 and R3 are separate resistors in parallel
$A=A_{1}+A_{2}+A_{3}$	A1, A2 and A3 are three ammeters in parallel
$V_{1}=V_{2}=V_{3}$	V1, V2 and V3 are three batteries in parallel

Effects of an Electric Current

Formula	Abbreviations	Mnemonic
$W=I^{2}Rt$	W = Heat given out by a wire I = Current R = Resistance t = Time

Speed, Displacement and Velocity

Formula	Abbreviations	Mnemonic
$v={\frac {s}{t}}$	v = Average velocity s = Displacement t = Time taken

Acceleration

Formula	Abbreviations	Mnemonic
$a={\frac {v-u}{t}}$	a = Average accleration v = Final velocity u = Initial velocity t = Time taken
$v=u+at$	a = Average accleration v = Final velocity u = Initial velocity t = Time taken	Given in log tables
$s=ut+{\frac {1}{2}}at^{2}$	a = Average accleration s = Displacement u = Initial velocity t = Time taken	Given in log tables
$v^{2}=u^{2}+2as$	v = Final velocity u = Initial velocity a = Average acceleration s = Displacement	Given in log tables

Force, Mass and Momentum

Formula	Abbreviations	Mnemonic
F = ma	F = Force m = Mass a = Acceleration
p = mv	p = Momentum m = Mass v = Velocity
$F={\frac {mv-mu}{t}}$	F = Force m = Mass v = Final velocity u = Initial velocity t = Time
$m_{1}u_{1}+m_{2}u_{2}=m_{1}v_{1}+m_{2}v_{2}$	m1 = Mass of object 1 u1 = Initial speed of object 1 v1 = Final speed of object 1 m2 = Mass of object 2 u2 = Initial speed of object 2 v2 = Final speed of object 2

Pressure and Gravity

Formula	Abbreviations	Mnemonic
$Density={\frac {Mass}{Volume}}$ i.e. $\rho ={\frac {m}{v}}$	p = Density m = Mass v = Volume	"Monkeys Drink Vodka" Triangle
$P={\frac {F}{A}}$	P = Pressure F = Force A = Area	Given in log tables
P = pgh	P = Pressure p = Density g = Gravity h = Depth (height)	Given in log tables

Magnetic Fields

Formula	Abbreviations	Mnemonic
$F=BIl$	F = Force B = Flux density of field I = Current in conductor L = Length of conductor	Bills are forceful
$F=qvB$	F = Force on particle q = Charge on particle v = Speed of particle B = Flux density of field
$\Phi =BA$	$\Phi$ = Magnetic Flux B = Magnetic Flux Density A = Area	$1Wb=1Tm^{2}$
$E=-{\frac {d\Phi }{dt}}$	Induced emf E = (Final flux - Initial flux) / (Time taken)