Equations

Question 1

Speed

Answer 1

Speed = distance / time

Question 2

Acceleration

Answer 2

Acceleration = final velocity - initial velocity / time

Question 3

Weight

Answer 3

Weight = mass x gravity

Question 4

Density

Answer 4

density = mass / volume

Question 5

Force

Answer 5

Force = mass x acceleration

Question 6

Hooke’s law

Answer 6

Force = spring constant x extension in metres

Question 7

Moment of a force

Answer 7

Moment of force = force x perpendicular distance from the pivot in metres

Question 8

Principle of moments

Answer 8

Total clockwise moment = total anti-clockwise moment

F1d1 = F2d2

Question 9

Work done

Answer 9

Work done = force x distance

Question 10

Kinetic energy

Answer 10

Kinetic energy = 1/2 x mass x velocity^2

Question 11

Gravitational potential energy

Answer 11

GPE = mass x gravity x height

Question 12

Conservation of energy applied to falling objects

Answer 12

Loss of gravitational potential = gain of kinetic

mass x gravity x height = 1/2 x mass x velocity^2

Question 13

Power

Answer 13

Power = work done / time taken

Power = energy transfer / time taken

Question 14

Efficiency

Answer 14

Efficiency = useful energy output / total energy input x 100

Question 15

Pressure

Answer 15

Pressure = force / area

Question 16

Pressure due to liquid

Answer 16

pressure = density x acceleration due to gravity x height

Question 17

Momentum

Answer 17

Momentum = mass x velocity

Question 18

Pressure and volume relationship (Boyle’s law)

Answer 18

pV = constant

p1 x V1 = p2 x V2

Question 19

Specific heat capacity

Answer 19

Heat energy = mass x specific heat capacity x change in temperature

Question 20

Specific latent heat of fusion

Answer 20

Lf = total heat / mass of liquid change

Question 21

Specific latent heat of vaporisation

Answer 21

Lv = total heat / mass of vapour change from liquid

Question 22

Wave equation

Answer 22

Velocity = frequency x wavelength

Question 23

Frequency

Answer 23

Frequency = 1 / time period of wave

Question 24

Refractive index n

Answer 24

N = sin i / sin r

N = speed of light in air or vacuum / speed of light in any other medium

N= 1/sin c
C is the critical angle

Question 25

Echo

Answer 25

Speed of sound waves = 2 x distance / time

Question 26

Current

Answer 26

Current = charge / time

Question 27

Resistance

Answer 27

Resistance = voltage / current

Question 28

Potential difference (or voltage)

Answer 28

Voltage = energy / charge

Question 29

Resistance in series

Answer 29

R = R1 + R2….

Question 30

Resistance in parallel

Answer 30

1/R = 1/R1 + 1/R2 …

Question 31

Potential divider

Answer 31

V1/V2 =R1/R2

V2 = (R2 / R1 + R2) x V

V1 = (R1 / R1 + R2) x V

Question 32

Electrical Power

Answer 32

Power = current x voltage

Question 33

Electrical energy

Answer 33

Electrical energy = current x voltage x time

Question 34

Transformer

Answer 34

Voltage in primary coil / voltage in secondary coil = No. of turns in primary coil / no. of turns in secondary coil

If 100% efficient
Power in = power out
Current in primary coil x voltage in primary coil = current in secondary coil x voltage in secondary coil

Question 35

Relative density

Answer 35

Density of substance / density of water