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Homework Help: Work done by gravity by Wonder Woman

  1. Oct 22, 2012 #1
    Work done against gravity by Wonder Woman

    1. The problem statement, all variables and given/known data
    Wonder Woman, whose mass is 52 kg, is holding onto the free end of a 13.0 m rope, the other end of which is fixed to a tree limb above. She is able to get the rope in motion so that she can reach a ledge when the rope makes a 60 degree angle with the downward vertical axis. How much work does Wonder Woman do against the force of gravity?


    2. Relevant equations
    W=mgdcos(θ) ...maybe?


    3. The attempt at a solution
    Honestly, I'm having a hard time even understanding the wording of the problem itself (ESL). Are they telling me she swung over to a ledge, and want me to calculate the work of gravity when she's by that ledge? I don't get it....some insight on what is being asked would be greatly appreciated.

    Thanks in advance,

    Filipe
     
    Last edited: Oct 22, 2012
  2. jcsd
  3. Oct 22, 2012 #2

    PeterO

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    I suspect the work done will simply equal the change in Gravitational potential energy compared to hanging vertically, and being on the ledge.
     
  4. Oct 22, 2012 #3
    Ohh...I feel so dumb now. lol.
    So, will it be just the change in potential energy for Δh?

    [STRIKE]So final equation is W=m*g*Δh=m*g*(30-30*cos(θ)) ?[/STRIKE]
    So final equation is W=m*g*Δh=m*g*(13-13*cos(θ)) ?

    Thanks
     
    Last edited: Oct 22, 2012
  5. Oct 22, 2012 #4

    PeterO

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    I think the figure [rope length] in the original was 13 not 30?
    I appreciate the ESL difficulty with written questions.
     
  6. Oct 22, 2012 #5
    Thanks for pointing that out! Fixed.
    I am the worst for making dumb mistakes like that.

    I appreciate your quick reply, I can now finish my homework. :)
     
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