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Homework Help: Simple sum of forces parachute problem

  1. Oct 17, 2011 #1
    a 64 kg parachutist falling vertically at a speed of 6.3 m/s impacts the ground, which brings him to a complete stop in a distance of .92 m. assuming constant acceleration after his feet first touch, what is the average force exerted on the parachutist by the ground?

    i know:
    Vf=0
    Vi=6.3
    delta Y = .92

    i used (Vfy)^2=(Viy)^2+2a(deltaY)

    and found a = -21.57

    i then used F=ma: F= (65)(-21.57)

    and got -1402 N

    is this right?
     
  2. jcsd
  3. Oct 17, 2011 #2

    SammyS

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    Correct method.

    Is the force exerted by the ground upward, or is it downward?
     
  4. Oct 17, 2011 #3
    i think the force exerted by the ground on the man is upward? should my answer be positive?
     
  5. Oct 17, 2011 #4

    SammyS

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    I would think so.
     
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