### Demos: 1N-11 Anvil and Balls

To test the elastic properties of various materials, balls of different compositions (steel, rubber, glass, Superball, Ping-Pong, lead, etc) are dropped from a common height onto a hard steel surface (anvil). The extent to which they bounce off the surface is related to their elastic properties.

Directions: Take each ball in turn and drop it from a predetermined height onto the anvil. Save the lead ball until last, since it is the most dramatic--it just hits and sits.

Suggestions for Presentation: Discuss with the class the common understandings of what one means by the term “elasticity.” If the balls are of different elasticity, what does this mean in a practical sense? How would you expect the different balls to bounce off the anvil?

In collisions, we have a parameter called the coefficient of restitution. Technically this parameter has to do with the interaction of two bodies, but by having the second body remain the same, we can tie the elasticity of the dropped objects to the coefficient of restitution. If the ball is dropped from a height h0 and rebounds to a height h, the coefficient of restitution for ball and plate the is given by

If you place a meter stick by the anvil you can get approximate values for h and h0.

Applications: To get the maximum transfer of momentum in a collision process, you want to select materials with high elasticity (high coefficient of restitution).

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Last Updated: May 9, 2016 11:44 AM