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Work Energy Theorem of a spring

  1. Nov 4, 2012 #1
    1. The problem statement, all variables and given/known data
    ZHW8r.png


    3. The attempt at a solution
    h2Yg4.jpg

    Is this correct? Is the change in potential energy Ufinal-Uinitial?

    My answer turns out to be a positive number, so intuitively does this mean that some of the kinetic energy went into potential and thus the final potential energy is greater than the initial?
     
  2. jcsd
  3. Nov 4, 2012 #2

    haruspex

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    Looks fine, but several things bother me.
    What is "kg = 0.5m"?
    Why are you told the initial speed of the disk?
    Seems to me that the disk does not have enough KE to travel two revolutions down the slope, and it won't recoil that far either. But I cannot think of another interpretation of the question.
     
  4. Nov 4, 2012 #3
    kg is the radius of gyration, it would be used to solve for the total KE which is the sum of the rotational and translational motion. This is given to throw the students off I think :P
     
  5. Nov 4, 2012 #4

    haruspex

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    OK, but that doesn't satisfy my last point. As far as I can see, the information given is inconsistent. It would not travel two whole revolutions, in either direction. (Would somebody check that?) Superfluous information is one thing, contradictory information quite another.
     
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