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Weekend


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September 20, 2002

Strange But True!

  • A weekly column of incidental information, off-the-wall observations and other random facts about the world.
    • By BILL SONES and RICH SONES, Ph.D.
    Special to the Journal

    Q. These daredevils love sport and action but maybe not math so much. Yet their lives hang on the following equation: MAXIMUM STRETCH LENGTH = W/K + THE SQUARE ROOT OF [(W x W)/(K x K) + (2 x W x L)/K]. Who are they?

    A. Bungee jumpers, and before they go jump off a bridge, tower or hot-air balloon, they (or the jump master) had better know their weight precisely. It's the W in the above equation (K = the cord's stiffness, L = initial cord length), and if you plug in the numbers you'll see that a jumper who's twice as heavy will stretch the cord by at least 40% more--no problem so long as cord mechanics and length are well chosen for the site, a potential tragedy otherwise. (DON'T TRY THIS! DON'T TRY THIS!)


     
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