Physics Formulae IGCSE

What is the formula for speed?

speed = distance / time

What is the formula for average speed?

average speed = total distance / total time

What is the formula for distance from speed?

distance = speed × time

What is the formula for time from speed?

time = distance / speed

What is the formula for acceleration?

a = (v − u) / t

What is the formula for final velocity from acceleration?

v = u + at

What is the formula for acceleration from velocity–time graph?

acceleration = gradient = Δvelocity / Δtime

What is the formula for distance from speed–time graph?

distance = area under speed–time graph

What is the formula for displacement from velocity–time graph?

displacement = signed area under velocity–time graph

What is the formula for density?

ρ = m / V

What is the formula for mass from density?

m = ρV

What is the formula for volume from density?

V = m / ρ

What is the formula for weight?

W = mg

What is the formula for gravitational field strength?

g = W / m

What is the formula for resultant force?

F = ma

What is the formula for mass from force?

m = F / a

What is the formula for acceleration from force?

a = F / m

What is the formula for momentum?

p = mv

What is the formula for impulse?

impulse = FΔt = Δp

What is the formula for force from change in momentum?

F = (mv − mu) / Δt

What is the formula for conservation of momentum?

total momentum before = total momentum after (isolated system)

What is the formula for moment of force?

moment = force × perpendicular distance from pivot

What is the formula for principle of moments?

sum of clockwise moments = sum of anticlockwise moments (equilibrium)

What is the formula for pressure?

p = F / A

What is the formula for force from pressure?

F = pA

What is the formula for pressure in a liquid?

Δp = ρgΔh

What is the formula for work done?

W = Fd (distance in direction of force)

What is the formula for kinetic energy?

E_k = ½mv²

What is the formula for gravitational potential energy change?

ΔE_p = mgΔh

What is the formula for power?

P = E / t = W / t

What is the formula for energy from power?

E = Pt

What is the formula for efficiency as decimal?

efficiency = useful energy output / total energy input

What is the formula for efficiency as percentage?

efficiency (%) = (useful energy output / total energy input) × 100

What is the formula for efficiency using power?

efficiency (%) = (useful power output / total power input) × 100

What is the formula for spring force (hooke’s law)?

F = kx (within limit of proportionality)

What is the formula for spring constant?

k = F / x

What is the formula for spring extension?

x = stretched length − original length

What is the formula for elastic potential energy?

E = ½kx² (linear spring)

What is the formula for terminal velocity condition?

resultant force = 0, so acceleration = 0

What is the formula for average force from momentum change?

F_average = Δp / Δt

What is the formula for kelvin temperature?

T(K) = θ(°C) + 273

What is the formula for celsius temperature?

θ(°C) = T(K) − 273

What is the formula for specific heat capacity?

c = ΔE / (mΔT)

What is the formula for thermal energy for temperature change?

ΔE = mcΔT

What is the formula for specific latent heat?

L = E / m

What is the formula for energy for change of state?

E = mL

What is the formula for gas pressure–volume law?

p₁V₁ = p₂V₂ (fixed mass, constant temperature)

What is the formula for gas volume–temperature law?

V₁/T₁ = V₂/T₂ (fixed mass, constant pressure; kelvin)

What is the formula for gas pressure–temperature law?

p₁/T₁ = p₂/T₂ (fixed mass, constant volume; kelvin)

What is the formula for general gas relation?

p₁V₁/T₁ = p₂V₂/T₂ (fixed mass; kelvin)

What is the formula for thermal power?

P = ΔE / t

What is the formula for wave speed?

v = fλ

What is the formula for frequency from wave speed?

f = v / λ

What is the formula for wavelength from wave speed?

λ = v / f

What is the formula for frequency and period?

f = 1 / T

What is the formula for period and frequency?

T = 1 / f

What is the formula for wave speed from period?

v = λ / T

What is the formula for refractive index (angles)?

n = sin i / sin r (from air into medium)

What is the formula for refractive index (speeds)?

n = speed of light in vacuum / speed of light in medium

What is the formula for critical angle?

sin c = 1 / n (medium to air)

What is the formula for angle of reflection?

angle of incidence = angle of reflection (from normal)

What is the formula for magnification?

magnification = image height / object height

What is the formula for magnification using distances (thin lens)?

magnification = image distance / object distance (magnitudes, thin lens)

What is the formula for echo distance?

distance to reflector = speed × echo time / 2

What is the formula for electromagnetic wave speed in vacuum?

c ≈ 3.0 × 10⁸ m/s

What is the formula for speed of light frequency relation?

c = fλ (in vacuum)

What is the formula for electric charge?

Q = It

What is the formula for current?

I = Q / t

What is the formula for potential difference?

V = W / Q

What is the formula for electrical work from charge?

W = QV

What is the formula for resistance?

R = V / I

What is the formula for ohm’s law?

V = IR (ohmic conductor at constant temperature)

What is the formula for electrical power?

P = IV

What is the formula for power using resistance and current?

P = I²R

What is the formula for power using voltage and resistance?

P = V² / R

What is the formula for electrical energy?

E = IVt

What is the formula for electrical energy using power?

E = Pt

What is the formula for series resistance?

R_total = R₁ + R₂ + …

What is the formula for parallel resistance?

1/R_total = 1/R₁ + 1/R₂ + …

What is the formula for two parallel resistors?

R_total = (R₁R₂) / (R₁ + R₂)

What is the formula for series current?

I_total = I₁ = I₂ = …

What is the formula for series potential difference?

V_total = V₁ + V₂ + …

What is the formula for parallel potential difference?

V_total = V₁ = V₂ = …

What is the formula for parallel current?

I_total = I₁ + I₂ + …

What is the formula for potential divider?

V_out = V_in × R_out / (R₁ + R₂) (series pair; across R_out)

What is the formula for electrical energy in kwh?

energy (kWh) = power (kW) × time (h)

What is the formula for cost of electricity?

cost = energy (kWh) × tariff per kWh

What is the formula for transformer turns ratio?

V_p / V_s = N_p / N_s (ideal transformer)

What is the formula for ideal transformer power?

V_p I_p = V_s I_s

What is the formula for transformer current ratio?

I_p / I_s = N_s / N_p (ideal transformer)

What is the formula for transformer efficiency?

efficiency (%) = output power / input power × 100

What is the formula for force on a current-carrying conductor?

F = BIL sin θ (uniform magnetic field)

What is the formula for magnetic flux density from force?

B = F / (IL) (wire perpendicular to field)

What is the formula for nucleon number?

A = Z + N

What is the formula for number of neutrons?

N = A − Z

What is the formula for radioactive decay after n half-lives?

N = N₀(½)^n

What is the formula for number of half-lives?

n = elapsed time / half-life

What is the formula for activity after n half-lives?

A = A₀(½)^n

What is the formula for corrected count rate?

corrected count rate = measured count rate − background count rate

What is the formula for count rate?

count rate = counts / time