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Homework Help: Magnitude of Net Force

  1. Sep 13, 2005 #1


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    When a 58 g tennis ball is served, it accelerates from rest to a constant speed of 49 m/s. The impact with the racket gives the ball a constant acceleration over a distance of 45 cm. What is the magnitude of the net force acting on the ball?

    I tried using Fnet=ma, but acceleration isn't given. So I tried to find acceleration by dividing the velocity by time, but time isn't given. Then I tried to use a kinematic formula without time in it to solve for acceleration. When I got my "answer", it wasn't right. What in the world am I doing wrong?
  2. jcsd
  3. Sep 14, 2005 #2


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    How much work has the force done on the ball?
  4. Sep 14, 2005 #3


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    For any acceleration, starting from rest, v= at and s= (1/2)at2.

    Here you are told that v= 49 m/s and s= 45 m/s2. You can solve those two equations for a and t. (Of course, you only need a.)
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