Motion, forces and momentum
Every equation in the syllabus, grouped by topic. Unmarked equations are for everyone; “Extended” means Supplement content, tested only on Papers 2, 4 and 6.
| Quantity | Formula |
|---|---|
| Speed | v = s ÷ t |
| Average speed | total distance ÷ total time |
| Acceleration Extended | a = Δv ÷ Δt |
| Weight | W = mg (g ≈ 9.8 N/kg) |
| Density | ρ = m ÷ V |
| Spring constant Extended | k = F ÷ x |
| Force Extended | F = ma |
| Moment | moment = force × perpendicular distance from the pivot |
| Momentum Extended | p = mv |
| Impulse Extended | impulse = FΔt = Δ(mv) |
| Resultant force Extended | F = Δp ÷ Δt |
Energy, work and power
| Quantity | Formula |
|---|---|
| Work done | W = Fd = ΔE |
| Power | P = W ÷ t = ΔE ÷ t |
| Kinetic energy Extended | Ek = ½mv² |
| Change in gravitational potential energy Extended | ΔEp = mgΔh |
| Efficiency Extended | (useful energy output ÷ total energy input) × 100% |
| Efficiency (power) Extended | (useful power output ÷ total power input) × 100% |
Pressure and thermal physics
| Quantity | Formula |
|---|---|
| Pressure | p = F ÷ A |
| Pressure in a liquid Extended | Δp = ρgΔh |
| Gas at constant temperature Extended | pV = constant |
| Temperature in kelvin | T (K) = θ (°C) + 273 |
| Specific heat capacity Extended | c = ΔE ÷ (mΔθ) |
Waves and light
| Quantity | Formula |
|---|---|
| Wave speed | v = fλ |
| Reflection | angle of incidence = angle of reflection |
| Refractive index Extended | n = sin i ÷ sin r |
| Critical angle Extended | n = 1 ÷ sin c |
| Speed of electromagnetic waves in a vacuum Extended | 3.0 × 10⁸ m/s |
Electricity and magnetism
| Quantity | Formula |
|---|---|
| Current Extended | I = Q ÷ t |
| Resistance | R = V ÷ I |
| Electrical power | P = IV |
| Electrical energy | E = IVt |
| e.m.f. and potential difference Extended | E = W ÷ Q, V = W ÷ Q |
| Resistors in series | R = R₁ + R₂ + … |
| Two resistors in parallel Extended | 1 ÷ R = 1 ÷ R₁ + 1 ÷ R₂ |
| Potential divider Extended | R₁ ÷ R₂ = V₁ ÷ V₂ |
| Power loss in cables Extended | P = I²R |
| Transformer | Vp ÷ Vs = Np ÷ Ns |
| Transformer, 100% efficient Extended | IpVp = IsVs |
Space physics
| Quantity | Formula |
|---|---|
| Orbital speed Extended | v = 2πr ÷ T |
| Hubble constant Extended | H0 = v ÷ d (≈ 2.2 × 10⁻¹⁸ per second) |
| Age of the Universe (estimate) Extended | d ÷ v = 1 ÷ H0 |
Units to know
| Quantity | Units |
|---|---|
| Density ρ | g/cm³, kg/m³ |
| Force F, weight W | N |
| Energy E, work W | J, kJ, MJ, kWh |
| Power P | W, kW, MW |
| Pressure p | N/m², N/cm², Pa (Extended) |
| Momentum p | kg m/s (Extended) |
| Impulse | N s (Extended) |
| Specific heat capacity c | J/(kg °C), J/(g °C) (Extended) |
| Charge Q | C (Extended) |
| Resistance R | Ω |
Volume can be given in dm³: 1 dm³ is one litre.
How to use this sheet
- Cover the Formula column and test yourself topic by topic until you can write every line.
- Learn each equation with its units: many marks are lost on units, not on the physics.
- You also need some maths: areas of a rectangle, triangle and circle, volumes of a block and a cylinder, and Pythagoras.
- Source: Cambridge IGCSE Physics 0625 syllabus for 2026–2028 (PDF).