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Homework Help: Ball clearing fence

  1. Sep 19, 2010 #1
    A batter hits a pitched ball when the center of the ball is 1.36 m above the ground.The ball leaves the bat at an angle of 45° with the ground. With that launch, the ball should have a horizontal range (returning to the launch level) of 112 m. (a) Does the ball clear a 7.65-m-high fence that is 102 m horizontally from the launch point? (b) At the fence, what is the distance between the fence top and the ball center?

    so i solved for the initial velocity which is 33.13m/s
    the i broke it up into its x and y components
    Vx=23.43 m/s
    Vy = 23.43 m/s

    since the range is 112m i found the time that it takes for the ball to go 112m

    t= x/Vx = 112m/23.43m/s

    i then found the time it takes to 102 m using the same method and got 4.35s

    so to find the height of the ball i did x=(23.43)(4.35)+1/2(9.8)(4.35)^2 = 9.2m

    so i thought that it would be 2.91m above the fence but thats wrong.
    where did i go wrong/?
     
  2. jcsd
  3. Sep 19, 2010 #2

    Doc Al

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    Staff: Mentor

    Did you consider the initial height of the ball?
     
  4. Sep 19, 2010 #3
    yes

    to figure out the distance between the ball and the fence

    i did (9.2+1.36)-7.65
     
  5. Sep 19, 2010 #4

    Doc Al

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    Staff: Mentor

    Your work looks good to me. What book is this from?
     
  6. Sep 19, 2010 #5
    halliday, fundamentals of physics 9e
    its a wiley plus problem
     
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