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Homework Help: Heat engine/max height person can climb

  1. Jun 13, 2006 #1
    Ok guys, I can't seem to get started on this one. A little starter would be nice if ya can...and I'll try from there.

    Assume that a hiker needs 4000 kcal of energy to supply a day's worth of metabolism. Estimate the maximum height the person can climb in one day, using only this amount of energy. As a rough prediction, treat the person as an isolated heat engine, operating between the internal temperature of 37 deg C and the ambient air temperature of 20 deg C.

  2. jcsd
  3. Jun 13, 2006 #2


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    Do you know the formula for the efficiency of a heat engine?
  4. Jun 13, 2006 #3
    e = 1 - Q(low)/Q(high)

    I think that is it....but don't know how this helps me.
  5. Jun 13, 2006 #4


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    Replace those Q's by T's, and you have what you need. Then you know what fraction of the stored energy can be put into useful work. All you need then is to know how much work it takes to go up a certain height. They probably want you to just use the work it takes to overcome gravity, ie, the potential energy change (although realistically, this is only a small fraction of the total work done, otherwise it would be possible to walk on a flat plane for miles without burning a calorie).
  6. Jun 13, 2006 #5
    OK......I'll try that and see what I come up with....thank you, you've been very helpful!!!!

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