Happy and Sad Balls (1R40.30)
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Two rubber balls that look similar but have different elasticities are dropped on a table. One bounces, one doesn't.
The "happy" ball is made from Polychloropene (Neoprene), has a high coefficient of restitution, and will bounce close to the height it was dropped from.
The "sad" ball is made from Polynorbornene (Norsorex), has a low coefficient of restitution, and won't bounce at all.
It's hard to see in the above photo, but the "happy" ball is shinier or more reflective than the "sad" ball, which has a matte surface.
1) Instructional Guide from Arbor Scientific.