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Thread: A person walks to the top of the hill

  1. #1 A person walks to the top of the hill 
    Junior Member
    Join Date
    Aug 2014
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    1
    A 75 kg person walks to the top of a 240 m high hill expending 5.6 x 10^5 J of energy/
    a. What was the potential energy of the person at the top of the hill?
    b. What is the efficiency of the person in walking up the hill?

    Solution to a.
    GPE = mgh. M = 75, G = 9.8 m/s, H = 240. ∴ 75 x 9.8 x 240 = 176400 J

    Solution to b.
    Efficiency = Energy out / Energy in x 100%. ∴ 176400 / 560000 x 100% = 31.5

    Is this correct? I am not quite sure...
    Thanks
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  2. #2  
    Senior Member
    Join Date
    Oct 2013
    Location
    UK
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    997
    Hi, welcome to the forum. This looks fine to me. Pretty inefficient machines we are.
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