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Homework Help: Applied force of a ball on a glove

  1. Jul 20, 2016 #1
    1. The problem statement, all variables and given/known data
    A 0.145 kg baseball traveling at 35.0 m/s strikes a catcher's mitt which, in bringing the ball to rest, recoils backwards 0.11 m. What was the average force applied by the ball on the glove

    2. Relevant equations
    Fnet=ma or F=ma

    3. The attempt at a solution
    I am honestly so lost with this and skeptic because I have caught a couple errors on this problem sheet. I have no clue on how to get the acceleration of the ball to find the other variables. It doesn't give you time or the final velocity .
  2. jcsd
  3. Jul 20, 2016 #2

    Simon Bridge

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    You need all three newton's laws to understand the problem - and the work-energy relation is a good place to start.
  4. Jul 20, 2016 #3


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    Yes it does:

    7. cessation or absence of motion:

    You want to find an acceleration from an initial velocity, final velocity and a distance, which of the SUVAT equations can do that?
  5. Jul 20, 2016 #4
    But we have not learned that unit yet. We are supposed to find the answer with what we know which is 1d kinematics and Newtons laws of motion.
  6. Jul 20, 2016 #5
    We aren't supposed to know any of these more advanced kinematic equations. Only Newtons laws of motion and the 3 main kinematic equations which are vf=vi+at, d=vit+1/2at2 and vf2+vi2+2ad. Also wouldn't the final velocity be equal to whatever it is when it bounces back 0.11m?
  7. Jul 20, 2016 #6

    Simon Bridge

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    That is correct. The problem statement says that, after the ball and mitt have recoiled 11m, they are "at rest".

    You can do the problem with ALL Newton's laws, and knowing those kinematic equations.
    Can you find an equation where acceleration is the only unknown?
  8. Jul 20, 2016 #7
    vf2+vi2+2ad. I just tried it now by putting the vf as 0, the vi as 35 and the d as 0.11, but I didn't get the answer.
    Edit: I even changed the vi to 0 assuming that the initial velocity is when the ball is in the glove. Still nothing.
    Edit #2: I managed to get the answer from a previous thought. I got a crazy high acceleration and didnt continue because I thought that it was too high to be true. But then I went back to it. vi=35 and vf=0 d=0.11. Get the acceleration and multiply that by the mass to get 807 N
    Last edited: Jul 20, 2016
  9. Jul 20, 2016 #8

    Simon Bridge

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    Please show your working.
    Note: "vf2+vi2+2ad" is incorrect.
  10. Jul 20, 2016 #9
    Thank you for your help!
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