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Homework Help: Kinetic Energy

  1. Jan 18, 2004 #1
    The question is:

    If a sprinter running at 10 meters per second could convert his
    kinetic energy into upward motion, how high could he jump?

    How do I solve this if I use the KE = 1/2 mv^2

    I dont know what the mass is?
     
  2. jcsd
  3. Jan 18, 2004 #2

    jamesrc

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    Imagine all of that kinetic energy converted into gravitational potential energy. If you solve for the height, I think you'll find that the mass of the sprinter cancels out.
     
  4. Jan 18, 2004 #3
    So are you saying I should:

    1/2 mv^2 = mgh
    1/2 v^2/g=h
    1/2(10^2/9.8)=5.1m

    The text book I have in no way explains this, if this is correct
    where can I get other sources of help on physics
     
  5. Jan 18, 2004 #4

    jamesrc

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    Yes, that's what I'm saying. I wouldn't expect your textbook to explain exactly the solution to this problem, especially if it is an exercise from there. As long as it explains about kinetic and potential energy, I wouldn't be too worried. The problem asks about an isolated "what-if" situation. What if instead of running at 10m/s, the sprinter jumped with an initial upward velocity of 10 m/s. I don't think there's anything more to read into the problem than that (which is why I don't think it's a problem if your textbook doesn't say anything about situations like this).
     
  6. Jan 19, 2004 #5
    Thanks, I was searching for an answer that I would never find.
     
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