School of Physics Lecture Demonstration Manual

Mb-5 Happy and Unhappy Balls

Published: Thursday 09 March 2006 - Updated: Thursday 24 March 2011


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


Happy and unhappy balls


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Happy and Unhappy Balls


Happy and Unhappy Balls


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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