How Does a Marathon Runner's Weight Impact Water Loss During a Race?

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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??

Problem
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:
 

Discussion

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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...

Daniel.
 


It is understandable why you might be confused about the relevance of the runner's weight in this problem. However, the weight of the runner does play a role in the amount of water that is lost through evaporation.

A person's weight is directly related to their body surface area, which is the area of their skin that is exposed to the environment. The larger the body surface area, the more sweat glands a person has and the more water they can lose through evaporation.

In this case, the runner's weight of 55kg indicates that they have a smaller body surface area compared to someone who may weigh more. This means that they have fewer sweat glands and may not lose as much water through evaporation as someone who weighs more.

Therefore, the weight of the runner does factor into the amount of water lost through evaporation during a marathon race. It may not be a significant difference, but it is still a relevant factor to consider in the overall calculation.