• Question: why do trampolines make you bounce higher then on the ground?

    Asked by dukesta to Stu, Jenni on 13 Jun 2011.
    • Photo: Jenni Tilley

      Jenni Tilley answered on 13 Jun 2011:

      Because they’re like giant elastic bands.

      Elastic bands are made of long chains of atoms tangled together like spaghetti in a bowl, To improve the strength of this material the tangled polymer chains are crosslinked together, producing a net-linke material. This produces a interesting spring-like behaviour: When the elastic band is stretched, the chains of atoms extend and the elastic deforms. However, the crosslinks
      holding the chains together resist this extension and pull the chains back into their original positions. This causes the rubber band to spring back to its original shape.

      This effect is not limited to trampolines – the soles of running shoes contain a layer of material that behaves in the same way (polyurethane). as runners deform their polyurethane shoes, the restoring force pulls the shoes back to their original shape, giving the runner a bit of a push as they do.

      This provides some insight into why polyurethane swim suits were so effective…http://news.bbc.co.uk/sport1/hi/other_sports/swimming/8161867.stm

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