Table of Mechanics Demonstration

List of Mechanics Equipment & Supplies

Lecture Demonstrations

Happy and Sad Balls, 1R40.30

Topic and Concept:




A bouncy ball and a non-bouncy ball are dropped from the same height with very different outcomes demonstrating the difference between elastic and inelastic collisions.



ID Number

Happy and Sad Balls

ME, Bay A2, Shelf #2


Important Setup Notes:

Setup and Procedure:

  1. Set balls in tray to be held until use.
  2. Drop the balls simultaneously from some arbitrary height. One ball will bounce (the happy ball) and the other won't (the sad ball).

Cautions, Warnings, or Safety Concerns:


At the moment just before impact, each ball has its own momentum. Upon collision with the ground, the nature of the momentum transfer will depend on the material from which each ball is made. If the ball allows for an elastic collision (the happy ball), the ball will bounce upward to the same height it was dropped (ideal case). If the ball allows for an inelastic collision, all of the momentum of the ball will be transferred to the ground. This demonstrates the difference between elastic and inelastic collisions.



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