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Homework Help: Simple Force Problem

  1. Feb 26, 2007 #1
    1. The problem statement, all variables and given/known data
    An 80 KG man is standing on the platform of mass 20 KG is lowering him self down using a massless cable passing over two pullies. If his downward acceleration is .2 M/S^2, find force exerted by the man on the cable.


    2. Relevant equations
    I thought it was a simple
    F=M*A


    3. The attempt at a solution
    F= (100 Kg) * (.2 m/s^2)
    F= 20 N
     
  2. jcsd
  3. Feb 26, 2007 #2
    That is correct, provided gravity is ignored.

    If you do not intend to ignore gravity, remember that gravity exerts a force of 9.8 N (g) at the surface of the Earth.
     
  4. Feb 26, 2007 #3
    I am and idot, thanks for the gravity tip also ther is a diagram I did not provide taht is very important, just out of curiosity do you put pictures on here using HTML type.

    Calculation is
    -980 + 3t=100kg*.2
    3t=-20+980
    t=320 N
    The reason it is 3t is because the diagram shows the rope connecting the celling and the platform/man 3 times with the two pullys)
     
  5. Feb 26, 2007 #4
    I believe HTML is disabled, although you could upload the image and use IMG tags, I believe.
     
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