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Homework Help: Marathon Runner Weight?

  1. Jan 22, 2005 #1
    Marathon Runner Weight????

    I have looked at the following problem and don't see how the weight of runner comes into play. I have solved the problem and my answer matches the one in the back of the book. What am I missing??

    A marathon runner has the average metabolism rate of about 950kcal/h during a race. If the runner has a mass of 55kg, estimate how much water she would lose to evaporation from the skin for a race that lasts 2.5h.

    My Solution
    Heat = metabolism rate x hrs = 2375 kcal

    Weight of water vaporized = Heat/Heat of Vaporation @ 20 C = 2375/585 = 4.1 kg = 4.1 liters :confused:
  2. jcsd
  3. Jan 22, 2005 #2


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    Homework Helper

    The answer is good...It's true,marathonist lose on avg 5Kg of water through sweat in a race.I don't know about that 55Kg,i think it enters in the equation which gives you the heat to evaporate at 37°...You used the figure for 20°.Not even dead,the human body wouldn't have 20°...

    Think about it...

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