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Bouncing a rubber ball with a hole in it

  1. Mar 29, 2004 #1

    ShawnD

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    As you all know, rubber balls (tennis balls) do not bounce good if there are holes in them. Why is that? I have 2 ideas as to what it is but i'm not sure which one.

    1. The rubber cannot compress properly so the ability for the rubber to store elastic energy is gone.
    2. The air inside of the ball usually provides constructive interference when the ball bounces back up. If the air can't compress, it can't provide that constructive interference.

    1 makes a lot of sense but I've been golf balls with huge cuts in them work perfectly fine.

    Thoughts?
     
    Last edited: Mar 30, 2004
  2. jcsd
  3. Mar 30, 2004 #2
    What kinds of rubber balls? You mean a ball that is originally hollow?

    If so, I think it's because of the air flow through the holes: when the ball is compressed, the air streams out very quickly (it's rather a pressure wave than a real "flow"), and vice versa. But this in-and-out flow comes together with an energy loss due to the streaming resistance of the holes. The crash has now strong "hysteresis" characteristics, meaning that the average force between ball and ground during compression is considerably larger than during decompression.

    Without the holes, the air can act as a very well "spring". (Interference??)
     
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