Force
A 2 kg object accelerates at 3 m/s². Find the net force.
F = ma = 2 × 3 = 6 N.
Physics Equations
A compact reference for introductory physics. Symbols and SI units are listed with each equation.
Mechanics
| Quantity | Equation | Units |
|---|---|---|
| Velocity | v = u + at | m/s |
| Displacement | s = ut + ½at2 | m |
| Velocity squared | v2 = u2 + 2as | m²/s² |
| Force | F = ma | N |
| Weight | W = mg | N |
| Momentum | p = mv | kg·m/s |
| Kinetic energy | KE = ½mv2 | J |
| Potential energy | PE = mgh | J |
| Work | W = Fd cos θ | J |
| Power | P = W/t | W |
| Density | ρ = m/V | kg/m³ |
| Pressure | P = F/A | Pa |
Electricity
| Quantity | Equation | Units |
|---|---|---|
| Ohm’s law | V = IR | V |
| Power | P = VI = I2R = V2/R | W |
| Charge | Q = It | C |
| Energy | E = QV | J |
| Series resistance | R = R1 + R2 + … | Ω |
| Parallel resistance | 1/R = 1/R1 + 1/R2 + … | Ω |
Waves and optics
| Quantity | Equation | Units |
|---|---|---|
| Wave speed | v = fλ | m/s |
| Period | T = 1/f | s |
| Snell’s law | n1 sin θ1 = n2 sin θ2 | — |
| Lens equation | 1/f = 1/u + 1/v | m |
| Magnification | m = v/u | — |
Thermodynamics
| Quantity | Equation | Units |
|---|---|---|
| Heat energy | Q = mcΔT | J |
| Ideal gas | PV = nRT | Pa·m³ |
| Efficiency | η = useful output / total input | — |
Worked examples
Ohm’s law
A 12 V supply drives 0.5 A through a resistor. Find R.
R = V/I = 12 / 0.5 = 24 Ω.
FAQ
What value of g should I use?
Use g = 9.8 m/s² unless your exam board specifies 9.81 or 10 m/s².
Are these equations enough for A-level?
These cover the core. A-level data booklets add topic-specific equations; check your board.
Last updated November 1, 2026. Formulas are checked against standard references. Read the editorial policy.