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Please help explain behaviour of squash balls

  1. Dec 8, 2011 #1
    Dear forum

    I have set AS physics (in england) coursework where the students drop squash balls at different temperatures and measure the bounce height. Yes, I know it is mentioned a lot but haven't so far found a good explanation.

    Their results will show that the higher temperature rubber balls bounce higher. They have seen a squash ball dropped (and bounced well!) when taken out of liquid nitrogen. I think it is because the squash ball had 'glassy' properties.

    I want to know how the students can explain how the balls bounce higher when heated?

    I want to avoid talking about air pressure in the ball - as this deviates from the behaviour of rubber materials.

    Some text books mention that rubber contracts with heat and will stiffen? Others say the rubber will become softer! And how would this relate to higher bounces?

    Does energy from inelastic collision with floor go into heating a cold rubber ball and so lower bounce? and so a warm rubber ball would receive less heating and more kinetic energy?

    How does heat effect the chains of molecules? Do warmer molecules behave more elastically?

    Would really appreciate your help.

    Kind regards

    Andy
     
  2. jcsd
  3. Dec 8, 2011 #2

    olivermsun

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    Science Advisor

    There is an article by Lewis, Arnold, and Griffiths which addresses some of these questions.

    Their conclusion by the way was that the air pressure is not particularly important, so it's mostly changes to the (lossy) behavior of the rubber that causes a warmer squash ball to bounce higher.
     
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