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Need help

  1. Oct 30, 2008 #1
    1. The problem statement, all variables and given/known data

    A tennis ball of with a mass of .045 kg and speed of 25 m/sec strikes a wall at an angle of 45 degrees and rebounds with the same spped at 45 degrees. What is the impulse given the wall?

    2. Relevant equations

    I= pf-pi/t

    3. The attempt at a solution

    I= mv-mv/t
    (.045)(25)-(-.045)(25)/1
    1.125-1.125/1
    I=2.25
    I know the answer is 2.1, but don't know how to get it.
     
  2. jcsd
  3. Oct 30, 2008 #2
    What do the letters stand for in this equation?
     
  4. Oct 30, 2008 #3
    The letters stand for Impulse = final momentum - the initial momentum/ time
     
  5. Oct 30, 2008 #4
    the impulse is the change in momentum. So the equation is
    change in momentum = (change in force) / time
    if I'm not mistaken.
     
  6. Oct 30, 2008 #5
    Another way of writing it is:

    Impulse = Force x time = change in momentum
     
  7. Oct 30, 2008 #6

    malawi_glenn

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