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Physics pulley problem

  1. May 3, 2009 #1
    1. The problem statement, all variables and given/known data

    we did a lab on pulleys. The weight lifted was 19.62 N. It rose 0.20 meter with us applying a lifting force of 11 N and pulling the rose a distance of 0.16.


    3. The attempt at a solution
    I tried to find the efficiency of the pulley, so E=work out/work in
    so work out=FD=(19.62)(0.20)=3.92
    and work in=FD=(11)(0.16)=1.76
    yet the work output cant be greater than the work input, so I'm clearly doing something wrong.

    Any ideas? Is it a math error or bad lab results? Any help would be great :)
     
  2. jcsd
  3. May 3, 2009 #2

    Doc Al

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    Staff: Mentor

    It's not a math problem. Those measurements don't make sense. How did you measure the applied force and distances?
     
  4. May 3, 2009 #3
    oh no. That means the whole lab is wrong, but I'm doing the math right?
    We measured the applied force with a spring scale and the distances with a ruler. i think the distances are completely wrong now...
     
  5. May 3, 2009 #4

    Doc Al

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    Staff: Mentor

    Yep, your math is fine. :frown:
     
  6. May 3, 2009 #5
    oh well. Thanks for the help though! Guess I'll have to start making up numbers
     
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