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Homework Help: Finding work for this problem

  1. Oct 18, 2008 #1
    1. The problem statement, all variables and given/known data

    Batman, whose mass is 101kg, is holding on to the free end of a 16 m rope, the other end of which is fixed to a tree limb above. He is able to get the rope in motion as only Batman knows how, eventually getting it to swing enough that he can reach a ledge when the rope makes a 80.4 degree angle with the vertical. The acceleration for gravity is 9.8m/s^2. How much work is done against the force of gravity in this maneuver? Answer in units of J.

    2. Relevant equations

    W= Frcos(theta)

    3. The attempt at a solution

    W= Frcos(theta)
    = (101*9.8)(16)(cos80.4)
    = 2641.08 J
    = wrong answer

    What am I doing wrong? From the looks of it, maybe the angle? If so what angle do I use and how do I find it?
  2. jcsd
  3. Oct 18, 2008 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    How much more energy does Batman have at the end of the process, compared to at the beginning? Where would that energy come from?
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