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A running Spit

  1. May 15, 2008 #1
    Inspired by this story.

    Would running before you spit increase the distance your spit travels? I figure, most of the energy comes from your mouth, and you'd probably stop at the end of your run, so would a "running start" increase the distance?
     
  2. jcsd
  3. May 15, 2008 #2
    I would say that it increases the distance, assuming that you spit first and then stop running. The reason is that the spit inside you already has the speed of your moving and when you spit you add to that speed. So by the time the spit hits the ground (which is independent of horizontal velocity, so same in both running and non running cases), it has traveled further.

    Think of it as pushing a barrel of a tall building vs pushing a barrel of a moving air-plane. Both of them seem to me be very common elementary physics problems, so I'm guessing you have come across them before. :)
     
  4. May 17, 2008 #3

    LURCH

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    Yes, it would increase the distance. This would be true whether you stop when you spit, or keep going. But of course, if you keep going, it will only increase the distance as measured by a stationary observer, your spit will not travel farther from you (indeed, it will not travel as far from yourself, as you would create a slight headwind by running.
     
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