School of Physics Lecture Demonstration Manual

Mb-5 Happy and Unhappy Balls

Published: Thursday 09 March 2006 - Updated: Wednesday 18 April 2007

Aim

To demonstrate the difference of coefficient of restitution of two balls that appear to be quite similar.

Apparatus

Happy and unhappy balls

Description

By holding the two balls at the same height, and releasing them, one will bounce back to a similar height of release, while the other ball will hardly bounce at all. The happy ball, the one with greater bounce, has a high coefficient of restitution. The unhappy ball has a low coefficient of restitution, thus absorbing most of the energy of the fall.

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