⚡ A-Level Physics
Physics Complete Cheatsheet
Motion, electricity, waves, thermodynamics and nuclear — all key formulas.
01
SI Units & Prefixes
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meter (m)
Length
kilogram (kg)
Mass
second (s)
Time
ampere (A)
Current
kelvin (K)
Temperature
mole (mol)
Amount
mega (M)
10⁶
MHz, MJ
kilo (k)
10³
km, kN
centi (c)
10⁻²
cm
milli (m)
10⁻³
mm, mA
micro (μ)
10⁻⁶
μm, μA
nano (n)
10⁻⁹
nm
02
Motion (SUVAT)
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PHYSICSSUVAT — 5 kinematic equations
v = u + at s = ut + 1/2 at^2 v^2 = u^2 + 2as s = 1/2(u+v)t s = vt - 1/2 at^2 g = 9.81 m/s^2 (free fall) Range: R = u^2 sin(2x)/g
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Choose equation with 4 variables you know/need. Always define positive direction.
03
Newton's Laws
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Newton 1st
F=0 → constant velocity
Inertia
Newton 2nd
F = ma
Newtons when m=kg, a=m/s^2
Newton 3rd
F_12 = -F_21
Equal+opposite reaction
Weight
W = mg
g=9.81 m/s^2
Momentum
p = mv
kg.m/s, conserved in collisions
Impulse
J = Ft = Dp
Change in momentum
Centripetal
F = mv^2/r
Toward centre of circle
Friction
f = uN
u=coefficient, N=normal force
04
Work, Energy & Power
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Work
W = Fs cos(x)
J = N.m, x=angle
Kinetic energy
KE = 1/2 mv^2
Joules
Gravitational PE
GPE = mgh
h above reference
Elastic PE
PE = 1/2 kx^2
k=spring constant
Power
P = W/t = Fv
Watts = J/s
Efficiency
n = useful/total x 100%
Conservation
KE1+PE1 = KE2+PE2
Elastic collisions only
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In inelastic collisions momentum is conserved but KE is NOT.
05
Waves & Optics
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Wave Properties
Wave speed
v = fl
f=Hz, l=wavelength in m
Period
T = 1/f
seconds per cycle
Speed of light
c = 3x10^8 m/s
in vacuum
Snell's Law
n1 sin(x1) = n2 sin(x2)
refraction
Refractive index
n = c/v
Transverse
Displacement perpendicular to travel. Light, EM waves.
Longitudinal
Displacement parallel to travel. Sound.
Constructive
Path diff = nl. Waves reinforce.
Destructive
Path diff = (n+1/2)l. Waves cancel.
Doppler effect
Apparent frequency change when source/observer moves.
06
Electricity
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PHYSICSCircuit laws
Ohm's Law: V = IR Power: P = IV = I^2 R = V^2/R Charge: Q = It Series: R_total = R1+R2, same I, V splits Parallel: 1/R = 1/R1+1/R2, same V, I splits Kirchhoff 1st: sum I at junction = 0 Kirchhoff 2nd: sum EMF = sum IR in loop Coulomb's Law: F = kq1q2/r^2 k=9x10^9
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Series: I constant. Parallel: V constant.
07
Magnetism
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Force on conductor
F = BIL sin(x)
B=field, I=current, L=length
Force on charge
F = qvB sin(x)
q=charge, v=velocity
Faraday's Law
EMF = -N*dPhi/dt
Induced EMF
Transformer
Vp/Vs = Np/Ns
turns ratio
Magnetic flux
Phi = BA cos(x)
Weber = T.m^2
08
Thermodynamics
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1st Law
dU = Q - W
Energy conserved: heat added minus work done
2nd Law
Entropy dS >= 0
Entropy of isolated system never decreases
Ideal Gas
PV = nRT
R=8.31 J/mol.K, T in Kelvin
Specific heat
Q = mc*dT
c=specific heat capacity J/kg.K
Latent heat
Q = mL
No temperature change during phase transition!
ℹ️
T must be in Kelvin for gas law calculations. K = degC + 273
09
Nuclear Physics
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Alpha (a)
Helium nucleus. Stopped by paper. Highly ionising.
Beta (b)
Fast electron. Stopped by aluminium. Medium ionising.
Gamma (g)
EM radiation. Stopped by thick lead. Least ionising.
Half-life
N = N0 x (1/2)^(t/t_half). Time for half to decay.
E=mc^2
Mass-energy equivalence. c=3x10^8 m/s
Fission
Large nucleus splits. Energy released. Nuclear reactors.
Fusion
Small nuclei join. More energy. Powers the Sun.
Binding energy
Energy to separate nucleus. Higher = more stable.
10
Mini Quizzes
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❓ Quiz 1
Which SUVAT equation does NOT include time?
v^2 = u^2 + 2as contains only v, u, a, s. Perfect when time is unknown.
❓ Quiz 2
What is the unit of electric charge?
Charge Q is in Coulombs. Q = It, so 1 C = 1 A x 1 s. Electron carries 1.6x10^-19 C.
❓ Quiz 3
The 1st Law of Thermodynamics states:
1st Law: dU = Q - W. Change in internal energy = heat added minus work done BY gas.