| A20-1 | Happy and unhappy balls |
| Purpose: | To demonstrate inelasticity. |
| Description: | The unhappy ball is made of a rubber called Norbomene polymer, which possesses excellent impact absorption properities. The happy ball is made of common neoprene. Although both balls are identical in shape, the unhappy ball has a small repulsive modulus of almost zero, while the happy ball rebounds very well under standard 10 - 30 degree C conditions. |
| References: | |
| Equipment: | happy and unhappy balls |