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Homework Help: Angular impulse of rolling ball

  1. Nov 3, 2012 #1
    In the following, we have a sliding sphere, when it meets a floor with friction.

    I want to use the angular impulse method to find an expression of the v when pure rolling starts.


    [sorry I have no idea how to type in latex.]

    This is obviously incorrect.
    But I cant find out what's wrong. anyone?
  2. jcsd
  3. Nov 3, 2012 #2
    Why is that obviously wrong? I at least could follow it. (Small note: you changed from r to R in the problem. Also I think Vi should equal Vi not Vi=V because if Vi=V that's like Vi=Vf, but that's more of a typo.)
    Last edited: Nov 3, 2012
  4. Nov 3, 2012 #3
    it's wrong cos it states that mv is larger tahn the impulse given.
  5. Nov 3, 2012 #4
    ?? Kind of following. Why does that matter? The value of mv can be bigger than the linear impulse in this problem. (Note: where mv=mVfinal)
  6. Nov 3, 2012 #5


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    It might become clearer if you properly distinguish initial and final linear speeds (u, v perhaps) and get the relationship between them.
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