Making Maths: Make a Pendulum

Stage: 2 and 3 Challenge Level: Challenge Level:1

Galileo, a famous inventor who lived about 400 years ago, came up with an idea similar to this for making a time measuring instrument. His idea came from watching a lamp swinging back and forth.

You will need:


  • String
  • Weights (any objects which you can tie to the string)
  • A piece of wood about $1.5$m long
  • A hook
  • Stopwatch

What to do:


  1. Tie a weight onto the end of the piece of string.
  2. Make a loop at the other end of the string.
  3. Screw the hook into the piece of wood and balance the wood between the backs of two chairs.
  4. Put the loop of string over the hook.

    You have now made a pendulum and can begin to experiment to make a minute timer from it.

    Pendulum between two chairs

  5. Start the weight swinging and time how long it takes to make $20$ swings. Use a stopwatch for this.
  6. Find a way to make the pendulum swing $20$ times in $20$ seconds.

Experiment with different size weights.
Try different lengths of string.
Can you turn your pendulum into an accurate minute timer?

This activity features in our December 2008 Advent Calendar.