The difference between an (almost) elastic and an (almost) inelastic collision.

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Teachable Topics:

  • Energy transfer
  • Collisions (elastic & inelastic)
  • Coefficient of Restitution


The amount of energy dissipated when an object collides with the floor depends on the material of the object. If little energy is dissipated, then the ball can bounce quite high, and we say the collision is mostly elastic. If a lot of energy is dissipated, then the ball bounces only very slightly, and the collision is said to be mostly inelastic.

The two balls in this demo are made from different materials. The "happy" ball is made from neoprene rubber and bounces high, while the "sad" ball barely bounces at all and is made from Norbornene (a polymer synthesized from ethylene cyclopentadiene).


  • "happy" ball
  • "sad" ball


  • Hold the happy and sad balls at the same height, then drop them together.