Appendix A: Physics equations

In solving quantitative problems, students should be able to recall and apply the following equations, using standard SI units.

Equations required for Higher Tier papers only are indicated by HT in the left hand column.

Equation number

Word equation

Symbol equation

1

weight=mass ×gravitational field strength (g)

W=m g

2

work done=force ×distance (along the line of action of the force)

W=F s

3

force applied to a spring=spring constant × extension

F=k e

4

moment of a force=force ×distance (normal to direction of force)

M=F d

5

pressure=force normal to a surfacearea of that surface

p= FA

6

distance travelled=speed ×time

s=v t

7

acceleration=change in velocity time taken

a= vt

8

resultant force=mass ×acceleration

F=m a

9 HT

momentum=mass ×velocity

p=m v

10

kinetic energy=0.5 ×mass ×speed2

Ek= 12m v2

11

gravitational potential energy=mass  ×gravitational field strength (g)×height

Ep=m g h

12

power= energy transferredtime

P= Et

13

power= work donetime

P= Wt

14

efficiency= useful output energy transfertotal input energy transfer

 

15

efficiency= useful power outputtotal power input

 

16

wave speed=frequency ×wavelength

v=f λ

17

charge flow=current ×time

Q=I t

18

potential difference=current ×resistance

V=I R

19

power=potential difference ×current

P=V I

20

power=current2 ×resistance

P=I2 R

21

energy transferred=power ×time

E=P t

22

energy transferred=charge flow ×potential difference

E=Q V

23

density= massvolume

ρ= mV

Students should be able to select and apply the following equations from the Physics equation sheet.

Equations required for Higher Tier papers only are indicated by HT in the left hand column.

Equation number

Word equation

Symbol equation

1 HT

pressure due to a column of liquid=height of column ×density of liquid ×gravitational field strength (g)

p=h ρ g

2

final velocity2 initial velocity2=2 ×acceleration×distance

v2 u2=2 a s

3 HT

force= change in momentumtime taken

F= m vt

4

elastic potential energy=0.5 ×spring constant ×(extension)2

Ee= 12 k e2

5

change in thermal energy=mass ×specific heat capacity ×temperature change

E=m c θ

6

period= 1frequency

 

7

magnification= image heightobject height

 

8 HT

force on a conductor at right angles to a magnetic field carrying a current=magnetic flux density ×current ×length

F=B I l

9

thermal energy for a change of state=mass ×specific latent heat

E=m L

10 HT

potential difference across primary coilpotential difference across secondary coil=number of turns in primary coil number of turns in secondary coil

VpVs= npns

11 HT

potential difference across primary coil ×current in primary coil=potential difference across secondary coil ×current in secondary coil

Vp Ip=Vs Is

12

For gases: pressure ×volume=constant

p V=constant