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What is the initial projectile speed of the ball?

  1. Jan 13, 2007 #1
    The pitcher in a slow-pitch softball game releases the ball at a point 3.0 ft above ground level. A stroboscopic plot of the position of the ball is shown in the figure below, where the readings are 0.25 s apart and the ball is released at t = 0. On the horizontal axis, x1 = 20 ft.


    (a) What is the initial speed of the ball?
    ft/s
    (b) What is the speed of the ball at the instant it reaches its maximum height above ground level?
    ft/s
    (c) What is that maximum height?
    ft


    i tried to find part c first. since i know that time is equal to 1.25 seconds i used deltay=.5at^2
    .5(32)(1.25)^2
    25 feet
    this did not work so I do not know what to do?
    any one with any help. thaks
     

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  3. Jan 13, 2007 #2

    hage567

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    Why are you using t=1.25s in your calculation? That isn't the time it takes the ball to get to maximum height.
     
  4. Jan 13, 2007 #3
    If you can answer (b), that will help you answer (c).

    Dorothy
     
  5. Jan 14, 2007 #4

    Gib Z

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    u=0 i think
     
  6. Jan 14, 2007 #5

    cristo

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    u can't be zero as the ball is pitched!
     
  7. Jan 14, 2007 #6
    i am still not getting the answer. I also tried time as 1.25/2 but this is stil not right?

    any one please
     
  8. Jan 15, 2007 #7

    hage567

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    1.25/2 is the time to the maximum height. The equation you were using gives the change in height from where it started. Don't forget it was 3 ft above the ground when it was thrown. So if you want the total height above the ground you have to take that into account.

    Does that help?
     
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