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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 = R 2 / R 2 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