“Happy and Sad Ball Set“

Product description

“Set of two black rubber balls, each 1-3/8" in diameter, appear to be identical in terms of appearance and mass but are manufactured from different types of rubber. When dropped on a hard surface from an equal height, the happy ball bounces high and the sad ball barely bounces at all. The happy ball also rolls faster than the sad ball. Provides an interesting and memorable demonstration for studying elasticity, kinetic energy, and polymer composition.“