Equations

Question 1

Average speed

Answer 1

Distance moved/time taken

m/s

Question 2

Acceleration

Answer 2

Change in velocity/time
a = (v-u)/t
m/s^2 = (m/s)/s

Question 3

Force

Answer 3

Mass x acceleration
N = kg x m/s^2
Or
Change in momentum/time
(kgm/s)/t

Question 4

Weight

Answer 4

Mass x acceleration due to gravity (g)

N = kg x 10

Question 5

Momentum

Answer 5

Mass x velocity

kgm/s = kg x m/s

Question 6

Moment

Answer 6

Force x perpendicular distance from pivot

Nm = N x m

Question 7

Efficiency

Answer 7

Useful energy output / total energy input

X 100 to get %

Question 8

Work done

Answer 8

Force x distance moved

Nm = n x m

Question 9

Gravitational potential energy

Answer 9

Mass x height x g

J = kg x m x g

Question 10

Kinetic energy

Answer 10

1/2 x mass x velocity^2

J = 1/2 x kg x m/s^2

Question 11

Stopping distance

Answer 11

Thinking distance + braking distance

Question 12

Power

Answer 12

Current x voltage

W = A (or I)x V

Question 13

Energy transferred

Answer 13

Current x voltage x time

J = A (or I)x V x t

Question 14

Voltage

Answer 14

Current x resistance

A x ohms

Question 15

Charge

Answer 15

Current x time

Coulombs = Amps x time

Question 16

Wave speed

Answer 16

Frequency x wavelength

M/s = F x lamda (in m)

Question 17

Frequency

Answer 17

1/time period

Question 18

Refractive index

Answer 18

sin(i)/sin(r)

Ratio, therefore has no units

Question 19

sin(critical angle)

sin(c)

Answer 19

1/refractive index

1/n

Question 20

Density

Answer 20

Mass/volume

kg/m^3 = kg/m^3

Question 21

Pressure

Answer 21

Force/area

Pascals = N/m^2

Question 22

Pressure difference

Answer 22

Height x density x g

m x kg/m^3 x g

Question 23

Pressure constants

Answer 23

p1/T1 = p2/T2

p1 x V1 = p2 x V2

Question 24

For transformers:

Answer 24

Primary or input voltage / secondary or output voltage = primary turns/secondary turns
Vp/Vs = np/ns
Input power = output power
VpIp = VsIs