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Formulae for Physics (Formulae in italics are not on the syllabus, but may still be
assessed)
Section 1: General Physics
1. speed (m/s) = distance (m)
time (s)
s=d
t
2. area under a speed-time graph = distance travelled
3. weight (N) = mass (kg) x gravitational field strength (m/s2)
W =mxg
4. density kg/m3) = mass (kg)
volume (m3)
ρ= m
V
5. force on a spring (N) = spring constant (N/m) x extension (m)
F=kxe
6. turning force (moment) (Nm) = force (N) x distance from pivot (m)
7. K.E (kinetic energy) (J) = ½ x mass (kg) x velocity (m/s) x velocity (m/s)
KE = ½ mv2
8. G.P.E (J) = mass (kg) x height (m) x gravitational field strength (m/s2)
GPE = mgh
9. efficiency = useful energy output
total energy input
x 100
10. work done (energy transferred) (J) = force (N) x distance (m)
W= Fxd
11/22. power (W) = energy transferred (J)
time taken (m)
12. pressure (N/m2) = force (N)
area (m2)
P= W
t
p= F
A
13. pressure in liquids (N/m2) = density (kg/m3) x gravity (m/s2) x depth (m)
p = ρgh
Section 2: Thermal Physics
14. (For a gas) initial pressure x initial volume = final pressure x final volume
P1V1 = P2V2
(for heating a state of matter):
15. heat added (J) = mass (kg) x specific heat capacity (J/kg/K) x change in temperature (°C)
Q = mcΔT
(for changing state)
16. heat (J) = mass (kg) x latent heat (J/kg)
Q = mL
Section 3: Wave Physics
17. wave speed (m/s) = frequency (Hz) x wavelength (m)
v = fλ
18. refractive index = speed in material 1
speed in material 2
19. refractive index = incident angle
refracted angle
n = v1
v2
n = sin i
sin r
Section 4: Electricity and Magnetism
20. current (A) = charge (C)
time (s)
I=Q
t
21. resistance (Ω) = potential difference (V)
current (A)
R=V
I
22/11. power (W) = potential difference (V) x current (A)
P = IV
(for resistors in series)
23. total resistance = resistance 1 + resistance 2... etc
Rt = R1 + R2
(for resistors in parallel)
24. see formula...
1 = 1 + 1
Rt
R1
R2
(for transformers)
25. primary voltage = number of primary coils
secondary voltage number of secondary coils
Vp
Vs
(for 100% efficient transformers)
26. primary power = secondary power
VpIp = VsIs
Section 5: Nuclear and Atomic Physics
27.
Z
X:
A
A = atomic (proton) number
Z = mass number
For alpha decay: A decreases by 2, Z by 4
For beta decay: A increases by 1, Z is unchanged
=
Np
Ns