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Homework Help: Force of a shot

  1. Sep 20, 2010 #1
    1. What is the average force exerted by a shot-putter on a 7.0 kilogram shot if the shot is moved through a distance of 2.8 meters and is released with a speed of 13 m/s?



    2. F=ma, x = vo t + 1/2 at^2, v=vo at



    3. I think you get time by using D = vt, but when I use this time and plug it into the distance equation above I get a weird answer. The real answer should be in the ballpark of 200 Newtons.
     
  2. jcsd
  3. Sep 20, 2010 #2
    ok I'm not sure how much calculus you know but the chain rule allows you to write:
    F=ma=m[tex]\frac{dv}{dx}[/tex][tex]\frac{dx}{dt}[/tex]=m[tex]\frac{dv}{dx}[/tex]v
    this means the F =mv*(change in velocity)/(change in position)


    However this gives me about 400 N so I might be forgetting something.
     
  4. Sep 20, 2010 #3
    Thanks for the response

    But I'm in an introductory physics course; calculus is a bit too much for me.

    I'll play around with the numbers some more.

    The problem seems really easy... I just can't get the right answer.
     
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