(ESSENTIAL) Equations for IGCSE physics (double award)

Question 1

State the equation for average speed

Answer 1

average speed = total distance travelled ÷ total time taken

Question 2

State the equation that relates acceleration, change in speed and time taken

Answer 2

a = Δv ÷ Δt

Δv means change in speed, Δt means change in time

Question 3

State the equation that relates the resultant force on an object to its acceleration

Answer 3

F = ma

Question 4

State the equation that relates the force applied to a spring to its extension

Answer 4

F = kx

Question 5

State the equation for kinetic energy

Answer 5

K.E. = ½mv²

Question 6

Give the equation for work done

Answer 6

Work done = Fd

Question 7

Give the equation for density

Answer 7

ρ = M ÷ V

can also be written as D = M ÷ V

Question 8

Give the equation for weight

Answer 8

W = mg

Question 9

State the equation for gravitational potential energy

Answer 9

G.P.E. = mgh

Question 10

State the equation for pressure

Answer 10

P = F ÷ A

Question 11

Give equation that relates the initial pressure and volume of a sample of gas to its final pressure and volume (Boyle’s law)

Answer 11

P₁V₁ = P₂V₂

Question 12

Give the equation for calculating the turning effect or ‘moment’ of a force

Answer 12

Moment = Fd

Question 13

Give the equation that relates charge and current

Answer 13

Q = It

Question 14

Give the equation that relates voltage and resistance

Answer 14

V = IR

Question 15

State the equation that relates power and energy transferred

Answer 15

power = energy transferred ÷ time

Question 16

State the equation for efficiency

Answer 16

efficiency = useful energy output ÷ total energy input

you can write efficiencies decimals, or you can muliply by 100 and leave an efficiency as a %

Question 17

State the equation that relates power, voltage and current

Answer 17

P = IV

Question 18

State the wave equation, that relates wave speed, wavelength and frequency

Answer 18

v = fλ

Question 19

Give the equation that relates the frequency of a wave to its time period

Answer 19

f = 1/T

or T = 1/f, which is the same equation, rearranged

Question 20

State the law of reflection

Answer 20

angle of incidence = angle of reflection

Question 21

Give the equation that relates the refractive index of a material to the angle of incidence and the angle of refraction

Answer 21

n = sin(i) ÷ sin (r)

Question 22

What is the equation that relates the refractive index of a material to the critical angle, for that material?

Answer 22

sin(c) = 1/n

Question 23

What equation can be used to calculate the pressure at a depth ‘h’ below the surface of a liquid?

Answer 23

P = ρgh

notice that density here is shown as the greek symbol ‘ρ’, NOT the letter ‘p’!

Question 24

What equation relates stopping distance, thinking distance and braking distance?

Answer 24

stopping distance = thinking distance + breaking distance

Question 25

What equation relates temperature in °C to temperature in K?

Answer 25

Temperature in °C = Temperature in K - 273

Question 26

Give the equation that relates instantaneous speed to change in distance and change in time

Answer 26

v = Δd ÷ Δt

Δd means change in speed, Δt means change in time