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Homework Help: Centripetal Net Force

  1. Nov 20, 2008 #1
    1. The problem statement, all variables and given/known data
    If you swing a ball in a horizontal circle around your head, what is the direction and magnitude of the net force acting on the ball?

    2. Relevant equations

    3. The attempt at a solution
    I said none because the ball is moving at a constant velocity. Is this correct? Or does the centripetal force come in to play?
  2. jcsd
  3. Nov 20, 2008 #2
    The direction of the force is inward, perpendicular to the velocity at any given moment of time.
  4. Nov 20, 2008 #3
    Is it a net force? If it were, wouldn't the ball be accelerating inward? Doesn't that force just offset the ball pulling on the string?
  5. Nov 20, 2008 #4
    good point.. I didn't see that "net" there.

    In that case, I do believe the -net- force is zero, as you said.
  6. Nov 20, 2008 #5


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    yes, it is , in the inward centripetal x direction.
    No, that's Newton's 3rd law, the string pulls on the ball, and the ball pulls on the string, with a force equal in magnitude and opposite in direction, always.
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