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Homework Help: Gravitational potential energy homework

  1. Oct 17, 2005 #1
    A climber's gravitational potential energy increases from 14000J to 21000J while climbing a cliff. She expends 18000J of energy during this activity. What is the efficiency of this process?

    A) 3%
    B) 39%
    C) 61%
    D) 97%


    Here is what I did.

    Wpg = ∆Epg = Epg2-Epg1 = 21000-14000 = 7000J

    % Eff = 100%(useful out)/total in = (100%)7000/18000 ≈ 39%


    The answer key says it is 61% though. Is the answer key wrong or did I miss something?
     
  2. jcsd
  3. Oct 17, 2005 #2

    Q_Goest

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    I'd agree with your answer. They key must be wrong.
     
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