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Homework Help: Related rates falling rock with shadow

  1. May 29, 2009 #1
    1. The problem statement, all variables and given/known data
    a light shines from the op of a pole 50ft high a ball is dropped from the same height from a point 30 feet away from the light , how fast is the shadow of the ball moving along the ground .5second later.

    So is the ball falling at 32ft/s^2
    would we set it up like 50/x=y/(x-30)
    x is the distance from the light pole to the end of the shadow and y is the heidght of the ball above the ground . is the balls rate 32t then we would take the deravative and plug every thing in , is my setup right .
  2. jcsd
  3. May 30, 2009 #2


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    Science Advisor
    Homework Helper

    Hi cragar! :wink:
    Yes, that's fine! :smile:

    Just one improvement …

    you've used similar triangles,

    but since the speed is 0 at the top, it will save time if instead of y you use the height of the ball below the top, and use a different pair of similar triangles :wink:
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