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Homework Help: Average Force Problem

  1. Jan 6, 2004 #1
    Helping my daughter with her homework (trying to help).
    A 65 kg parachuter hits the beach with a speed of 4.0 m/s, making a 0.2 m deep indentation in the sand. With what average force did the parachuter hit the sand?

    From what I found in the text it seems you need a time (which they don't provide). How about some clues?
     
  2. jcsd
  3. Jan 6, 2004 #2
    You should be able to calculate the average acceleration that the parachuter experienced as he moved through the .2M of sand. The change in velocity was -4.0 m/s through that .2m of sand. From there the average force should be easily calculated given the mass of the parachuter. I wouldn't think knowing the time is absolutely necessary but there is always more than one way to solve a problem.

    Hope this helps.
     
  4. Jan 6, 2004 #3
    If you wanted to calculate the time first and then work from there,

    [tex] t = \frac{2 D}{V} [/tex]

    Then you can calculate the acceleration from the velocity and time and then the force from there.
     
  5. Jan 6, 2004 #4
    I hope what I posted is helping you solve your problem. I have to leave now but if you are still having difficulty, just post where you are stuck and someone will help out.

    Good luck. :smile:
     
  6. Jan 6, 2004 #5
    Thanks a lot for the help, we solved the problem just now.
     
  7. Jan 6, 2004 #6
    My two cents:

    [tex]\frac{1}{2}mv^2=Fd[/tex]

    Doug
     
  8. Jan 6, 2004 #7
    That's a great solution which I also considered but since Forgo mentioned time I thought maybe I should stick with calculating the acceleration. I should have asked what his daughter was actually studying in relation to that problem.
     
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