1R40.30-Happy and Sad balls


Video: Watch this demo

Instructor’s video

Description: This demonstration shows different coefficients of restitution using the happy and sad balls.


  • Happy and Sad balls

Demonstration Procedure:

  1. Show that the balls are very similar, in shape, feel, and weight.
  2. Drop the happy ball. Note that it bounces up high.
  3. Drop the sad ball. Note that it does not bounce much.
  4. Explain that this is due to different coefficients of restitution, where a coefficient closer to 1 corresponds to a greater restitution and a higher bounce.