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Physics Equations

These are all of the equations you used to need to recall for Physics examinations... at each stage it was assumed you remembered the ones from the previous stage... so it was worth transferring them properly to your mental 'hard drive'!

The English examination boards now GIVE you equations - so you no longer get marks for recalling them. However, I would argue that actually knowing them makes it easier for you to explain a physics principle.

For example if you KNOW that F=ma, then, in answer to, 'What comprises evedence of a force acting?', you know that a net force will make a body accelerate.

Having a mathematical mind myself I find learning equations to be a shorthand way of learning Physics!

Make sure you know the correct units.......... all units to be used in equations should be in their basic form (no prefixes) - EXCEPT mass - that is kg!

Remember to take care when you write the equation letters... they are symbols NOT part of your handwriting!
Special care with I for current it shouldn't be possible to confuse it with l for length or 1 (the number one)!

Equation in words	Symbolic representation	Year	Key Stage
speed = distance travelled time taken	v = d/t	Y7	KS3
acceleration = change in velocity time taken	a = Dv/t	Y8	KS3
density = mass volume	r = m/V	Y7	KS3
force = mass x acceleration	F = ma	Y9	KS3
work done = force x distance moved in the direction of that force	W = Fs	Y9	KS3
momentum = mass x velocity	p = mv	Y12	AS
power = energy transferred time taken	P = E/t	Y8	KS3
power = work done time taken	P = W/t	Y9	KS3
weight = mass x gravitational field strength	w = mg	Y7	KS3
kinetic energy = half x mass x (velocity squared)	E_K= ¹/₂mv²	Y12	KS4
change in gravitational potential energy = mass x gravitational field strenth x difference in height	DGPE = mgDh	Y9	KS3
pressure = force applied contact area	P = F A	Y7	KS3
Gas Law: pressure x volume of a gas = number of moles x molar gas constant x absolute temperature	pV = nRT	Y12	AS
Gas Law: combination of Boyle's Law and Charles' Law	P₁V₁ = P₂V₂ T₁ T₂ _{NB Temperature MUST be in Kelvin}	Y11	KS4
charge = current x time	DQ = IDt	Y10	KS4
Ohm's Law: Potential difference = current x resistance	V = IR	Y8	KS3
Ohm's Law applied to the full circuit: Electromotive force = current x (sum of the circuit resistance and the internal resistance of the cell)	EMF = I(R + r)	Y12	AS
power = current x potential difference	P = I V	Y8	KS3
energy transferred in a component = charge passing through it x potential difference acorss it	W = QV	Y10	KS4
resistance = resistivity x length cross sectional area	R = r l A	Y12	AS
wavespeed = frequency x wavelength	v = fl for electromagnetic radiation v = c giving: c = fl	Y8	KS3
centripetal force = mass x speed² radius of path	F_C = mv² r	Y13	A2
Electrical energy changed into heat = potential difference x current x time	E = VI t	Y9	KS3
Inverse square law for force on a mass in a gravitational field of another mass: Force is proportional to the product of the masses and inversely proportional to the square of the distance between them	F_G = - G m₁ m₂ r² NB the minus sign indicates it is ALWAYS attractive	Y13	A2
Inverse square law for force on a charge in an electric field of another charge: Force is proportional to the product of the charges and inversely proportional to the square of the distance between them	F_E= 1 Q₁ Q₂ 4pe0 r² NB the overall sign indicating wherther it is attractive (negative) or repulsive (positive) comes from the signs of the charges. Also, although the constant of proportionality is complex it is a similar relationship to above.	Y13	A2
capacitance = charge stored potential difference	C = Q V	Y13	A2
ratio of the voltages across the coils of a transformer = the ratio of the turns on the coils	V1 = N1 V2 N2 NB the 1 could be P for primary and the 2 could be s for secondary - it doesn't matter which is which!	Y11	KS4

LOJ November 2000/revised October 2001/revised November 2002 and November 2010

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Physics Equations

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