Physics equations - Double award IGCSE 2025

Average speed (m/s)

distance (m) / time (s)

s = d/t

Average velocity (m/s)

displacement (m) / time (s)

v = s/t

Acceleration (m/s)^2

final velocity (m/s) - initial velocity (m/s) / time (s)

a = v-u/t

Weight (N)

mass (kg) x gravitational field strength (m/s)^2

Earths gravitational field strength: 10 (m/s)^2

F = mg

Force (N)

Mass (Kg) x acceleration (m/s)^2

F = ma

Density (Kg/m)^3

mass (kg) / volume (m)^3

p = M/V

Hookes Law (Force (N))

constant (Nm) x extension (m)

F = kx

Pressure (Pa)

Force (N) / area (m)^2

P = F/A

Fluid pressure (Pa)

density (kgm)^3 x gravitational field strength (ms^2 or Nkg) x height (m)

P = pgh

Work (J)

Force (N) x Distance moved (m)

change in E = Fd

Power (W)

work done (J) / time (s)

P = change in E/t

Kinetic Energy (J)

1/2 x mass (kg) x velocity^2 (m/s)

KE = 1/2mv^2

GPE (Gravitational potential energy) (J)

mass (kg) x gravitational field strength (m/s^2 or Nkg) x height (m)

GPE = mgh

Efficiency (%)

(useful power output (W) / total power input (W)) x100

Efficiency = POut/PIn

Efficiency (%)

(useful energy output (J) / total energy input (J)) x100

Efficiency = EOut/EIn

Moment (Nm)

force (N) x perpendicular distance from pivot (m)

M = Fd

Sum of clockwise moments (Nm) = Sum of anti clockwise moments (Nm)

F1 x D1 = F2 x D2

current (A)

charge (c) / time (s)

I = Q/t

Voltage (V)

energy transferred (J) / charge (c)

V = E/Q

Voltage (V)

current (A) x resistance (Ohm)

V = IR

Power (W)

current (A) x voltage (V)

P = IV

Power (W)

current^2 (A) x resistance (Ohm)

P = I^2 x R

Energy transferred (J)

current (A) x voltage (V) x time (s)

energy transferred = IVt

Energy transferred (J)

power (W) x time (s)

energy transferred = Pt

Resistors in series: Total Resistance (Ohm)

total resistance (Ohm) = sum of individual resistors (Ohm)

Total = R1 + R2 + R3...

Resistors in parallel

1/total resistance (Ohm) = 1/sum of individual resistors (Ohm)

1/Rtotal = 1/R1 + 1/R2 + 1/R3....

Resistance (Ohm)

resistance (Ohm/m) x length (m) / area (m^2)

area: pi x r^2

R=pl/A

Transformers:

voltage in secondary coil (v) / voltage in primary coil (V) = turns on secondary coil / turns on primary coil

Vs/Vp = Ns/Np

Transformers:

voltage in primary coil (V) / voltage in secondary coil (V) = current in secondary coil (A) / current in primary coil (A)

Vp/Vs = Is/Ip

Wave speed (m/s)

frequency (Hz) x wavelength (m)

c = fλ

Frequency (Hz)

1/Period (s)

F = 1/T

Refractive index

sine of angle of incidence/ sine of angle of refraction

n = sin(i)/sin(r)

Refractive index

speed of light in vacuum/speed of light in material

n = cy/cm

Refractive index

1/sine of critical angle

n = 1/sinc

Radioactive alpha decay

Radioactive beta decay

Radioactive gamma decay

Energy (J)

mass defect (kg) x speed of light^2

E = mc^2