# physics-equations ```IGCSE PHYSICS EQUATIONS by Samuel Lees
speed = distance / time
Acceleration = (final speed – initial speed) / time
Acceleration due to gravity in a vacuum = 2 &times; height dropped / time2
Force = mass &times; acceleration
Weight = mass &times; acceleration due to gravity
Density = mass / volume
Terminal velocity: weight = air resistance
Hooke’s law: Force = extension &times; spring constant
Moment of a force = force &times; distance
Equilibrium: total clockwise moment = total anti clockwise moment
Work done = force &times; distance
Kinetic energy = &frac12; &times; mass &times; velocity2
Gravitational potential energy = mass &times; acceleration due to gravity &times; height
Law of conservation of energy: loss of Ep = gain of Ek and gpe = ke
Power = work done / time taken or energy transferred / time taken
Efficiency = useful energy output / total energy input &times; 100%
= useful work done / total energy input &times; 100%
= useful power output / total power input
Pressure = force / area
Hydrostatic pressure = density of liquid &times; height &times; acceleration due to gravity
Atmospheric pressure = 105Pa = 760mmHg = 1000mb
Boyle’s law: p1 &times; v1 = p2 &times; v2
Charle’s law: Volume / KELVIN temperature = constant so...
V1 / T1 = V2 / T2
Pressure law: p/T = constant so...
P1 / T1 = P2 / T2
Specific heat capacity = heat energy / (temperature change &times; mass)
Thermal capacity = mass &times; specific heat capacity
Specific latent heat of fusion or vaporization = energy / mass
Speed of wave = frequency &times; wavelength
Frequency = 1 / time period of wave
Law of reflection: angle of incidence = angle of reflection
Refractive index = sin(i) / sin(r) or speed of light in vacuum / speed of light in medium
Critical angle = sin-1(1/refractive index)
Echo: speed of sound wave = 2 &times; distance / time taken
Charge = current &times; time
Ohm’s law: Voltage = current &times; resistance
Voltage = energy / charge
Resistance = resistivity &times; length / area
Resistance in series: Rtotal = R1 + R2 + R3
Resistance in parallel = (1/ Rtotal) = (1/R1) + (1/R2) +(1/R3)
Potential divider:
V1 / V1 = R 2 / R 2
V2 = R2 / Rtotal &times; Vin
V1 = R1 / Rtotal &times; Vin
Power = voltage &times; current
Power lost in a resistor = resistance &times; current2
Power = energy / time
Transformers: robots in disguise
Input voltage / output voltage = number of primary coils / number of secondary coils
Power in primary coil = power in secondary coil so...
Current 1 &times; Voltage1 = Current2 &times; Voltage2
Or
Current1 / Voltage1 = Current2 / Voltage2
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