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Homework Help: Force Average

  1. Jan 22, 2008 #1
    1. The problem statement, all variables and given/known data

    A tennis ball has a mass of 0.057 kg. A professional tennis player hits the ball hard enough to give it a speed of 52 m/s (about 117 miles per hour.) The ball moves toward the left, hits a wall and bounces straight back to the right with almost the same speed (52 m/s). As indicated in the diagram below, high-speed photography shows that the ball is crushed about 2 cm at the instant when its speed is momentarily zero, before rebounding.

    Assume that the large force the ball exerts on the wall is approximately constant during contact.
    What is the average speed of the ball during the period from first contact with the wall to the moment the ball's speed is momentarily zero?
    26 = m/s
    How much time elapses between first contact with the wall, and coming to a stop?
    7.69e-4 seconds

    What is the magnitude of the average force exerted by the wall on the ball during contact?

    2. Relevant equations

    change in momentum = fnet*deltat.

    3. The attempt at a solution
    1927.18 N
    -1927.18 N
    963.59 N
    -963.59 N
  2. jcsd
  3. Jan 23, 2008 #2
    use the concept of impulse and proceed...
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