1D50.40-Pail of Water


Video: Watch this demo

Description: As a pale of water is spun in a circle, the water does not fall out. This is because the string provides a centripetal force, while the inertia of the pale of water (Newton’s first law) causes an apparent “centrifugal force”, which keeps the water in the pale.

Note: If you go too slow, the water will fall out.


  • Metal pale with rope tied to the handle
  • Water

Setup Procedure:

  1. Check to make sure strings are securely attached.
  2. Can fill the pale ahead of time, or leave for professor to fill in class. Ask what is preferred.

Demonstration Procedure:

  1. Carefully start swinging the water-filled pale.
  2. Get it going as fast as possible, as soon as possible.
  3. When stopping, try to stop gradually so as to avoid spilling water all over the floor. You have to use some physics intuition to get the hang of this!