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Force on ball

  1. Oct 4, 2006 #1
    A baseball pitcher throws a ball straight up into the air at a speed of 21.0 m/s. In the process, he moves his hand through a distance of 1.40 m. If the ball has a mass of 0.150 kg, find the force he exerts on the ball to give it this upward speed.

    My problem is that I don't know where to use the 1.40m. I assume I have to find the acceleration somehow and then plug it into F=ma but every method I try seems to fail. Thanks for the help.
     
  2. jcsd
  3. Oct 4, 2006 #2

    Doc Al

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    Staff: Mentor

    What have you tried? You have the initial and final speed and the distance; that's all you need to find the acceleration. (You may need to review your kinematic equations.)
     
  4. Oct 5, 2006 #3
    I used V^2=Vo^2 +2a(delta)x

    and found acceleration to be 157.5.

    then i used F=ma= (.150)*(157.5) abd got the answer to be 23.625. Apparently this is within 10% of the correct answer but not quite right. Any ideas what's wrong?
     
  5. Oct 5, 2006 #4

    Doc Al

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    Staff: Mentor

    You are asked to find the force the pitcher exerted on the ball. You calculated the net force. What other force acts on the ball?
     
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