1D50.40 Pail of Water


Forces in circular motion


A pail of water is swung in a full circle and the water does not fall out when the pail is upside down.



  • [1] Pail of water
  • Packing chips (optional)

Classroom Assembly

  1. Fill the pail about 1/3 full with water.

Important Notes

  • Practice this demo in advance. Confidence and a smooth motion are required.


  1. Swing the pail vertically, starting with a low amplitude and working up to large amplitudes.
  2. Continue to increase the amplitude of the swing until the pail swings in a full circle.
  3. (Optional) You may use packing chips instead of water to show that the chips fall out if the pail is stopped when upside down.

Additional Resources


  • PIRA 1D50.40


  • Don't attempt this at home!

Last revised

  • 2018


Related AV

Related demos

  • Waiter's Tray
  • Coin on a Coathanger

If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.