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Homework Help: Force -displacement graph question

  1. Nov 15, 2012 #1
    1. The problem statement, all variables and given/known data
    A crate, having a mass of 45 kg is pulled steadily upwards by tw ropes through a height of 12 m. Each rope has mass of 0.75 kg/m. Draw the F-d graph and determine the work done in pulling the crate 12 m.

    3. The attempt at a solution
    Alright....

    so we know that we are starting with
    m1 = 45 kg
    m2 = 0.75kg/m x 12 m
    m2 = 9 kg x2
    m2 = 18 kg

    Now we need to find the force that it will have initially ...

    Fn = mg
    Fn = (18 kg + 45 kg)(9.8m/s^2)
    Fn = 617.4 N

    Now after the crate has been pulled 12 m ...
    it'll only have m1 attached which is 45 kg

    Fn=mg
    Fn=(45kg)(9.8m/s^2)
    Fn=441 N

    Now i made this graph...

    http://s1176.beta.photobucket.com/user/LolaGoesLala/media/ih.jpg.html

    Then i used this formula..

    W = (A+B/2)(d)
    W = (617.4 N+ 441 N/2)(12 m)
    W =6350.4 J
     
  2. jcsd
  3. Nov 16, 2012 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    OK that's great - did you have a question?
     
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