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October 04, 2025, 03:18:39 pm
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Author Topic: Energy used  (Read 836 times)  Share 

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Studyinghard

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Energy used
« on: April 12, 2011, 06:03:38 pm »
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A person is running up a gentle hill, going up a vertical height of 18 m in 2 minutes. Assuming that the efficiency for this activity is 25%, and the person's weight is 700 newton, what is the energy used (metabolised) by the person to undertake this activity? Answer in joule.

25200 J , is it right?
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xZero

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Re: Energy used
« Reply #1 on: April 12, 2011, 06:23:53 pm »
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w = mgΔh
w = 700 x 18
w = 12600J

Since the efficiency is 25%

Energy used = w/0.25 = 50400J

I don't think the time affects the energy used, thought it does affect the power in J/s
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schnappy

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Re: Energy used
« Reply #2 on: April 12, 2011, 06:29:12 pm »
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'energy used' = 0.25*Work = mgh
0.25*Work = 700*18 = 12600
Work = 50,400 J

Do you have the answer? My answer to these is contradicting most other answers i've read.

Edit: Aww beaten :(
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