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IGCSE PHYSICS EQUATIONS by Samuel Lees

speed = distance / time

Acceleration = (final speed – initial speed) / time

Acceleration due to gravity in a vacuum = 2 × height dropped / time2

Force = mass × acceleration

Weight = mass × acceleration due to gravity

Density = mass / volume

Terminal velocity: weight = air resistance

Hooke’s law: Force = extension × spring constant

Moment of a force = force × distance

Equilibrium: total clockwise moment = total anti clockwise moment

Work done = force × distance

Kinetic energy = ½ × mass × velocity2

Gravitational potential energy = mass × acceleration due to gravity × 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 × 100%

= useful work done / total energy input × 100%

= useful power output / total power input

Pressure = force / area

Hydrostatic pressure = density of liquid × height × acceleration due to gravity

Atmospheric pressure = 105Pa = 760mmHg = 1000mb

Boyle’s law: p1 × v1 = p2 × 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 × mass)

Thermal capacity = mass × specific heat capacity

Specific latent heat of fusion or vaporization = energy / mass

Speed of wave = frequency × 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 × distance / time taken

Charge = current × time

Ohm’s law: Voltage = current × resistance

Voltage = energy / charge

Resistance = resistivity × length / area

Resistance in series: Rtotal = R1 + R2 + R3

Resistance in parallel = (1/ Rtotal) = (1/R1) + (1/R2) +(1/R3)

Potential divider:

V1 / V1 = R2 / R2

V2 = R2 / Rtotal × Vin

V1 = R1 / Rtotal × Vin

Power = voltage × current

Power lost in a resistor = resistance × 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 × Voltage1 = Current2 × Voltage2

Or

Current1 / Voltage1 = Current2 / Voltage2

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