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Homework Help: Elastic Collision: Contact Time?

  1. Oct 31, 2009 #1
    1. The problem statement, all variables and given/known data
    A handball of mass 668 grams is thrown straight against a wall with a speed of 13.36 m/s. It rebounds straight back out with the same speed. The average force exerted on the wall by the ball is 12 N.

    How long is the ball in contact with the wall?


    2. Relevant equations
    FΔt = mΔv (?)


    3. The attempt at a solution
    m = 0.668 kg, Δv = 0 m/s, F = 12N
    With the equation I used, the answer I get is 0 s, but the answer isn't 0 s.

    Can anyone tell me what the correct equation to use is? Or what I'm doing wrong?
     
  2. jcsd
  3. Oct 31, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You are calculating Δv incorrectly. Don't forget to take direction into account.
     
  4. Oct 31, 2009 #3
    Thank you! That should have been so obvious. I got it right this time.
     
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