AQA A Level Physics

Revision Notes

6.2.5 Period of Simple Pendulum

Period of Simple Pendulum

  • A simple pendulum is another type of simple harmonic oscillator
    • The pendulum consists of a string and a bob (a weight, generally spherical) at the end
  • The time period of a simple pendulum is given by:

Period of Pendulum Equation _2

  • Where:
    • T = time period (s)
    • L = length of string (m)
    • g = gravitational field strength (N kg-1)


  • Length L is taken from the pivot to the centre of mass of the bob
  • Normally, the bob is taken as a point mass, so l is just the length of the string


  • The time period of a pendulum does depend on the gravitational field strength, meaning its period would be different on the Earth and the Moon
  • The limitation with this formula is that it only works for small angles from the equilibrium point (~10°)

Worked Example

Calculate the time period of a simple pendulum on the Moon, if on Earth it has a time period of 7 s.

g on the moon is 1/6 of that on Earth.

Period of Pendulum Worked Example_3


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