Answer: Keeping Your CoolA 68 kg cyclist is pedaling down

Chapter , Problem 8P

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Problem 8P

Keeping Your Cool

A 68 kg cyclist is pedaling down the road at 15 km/h, using a total metabolic power of 480 W. A certain fraction of this energy is used to move the bicycle forward, but the balance ends up as thermal energy in his body, which he must get rid of to keep cool. On a very warm day, conduction, convection, and radiation transfer little energy, and so he does this by perspiring, with the evaporation of water taking away the excess thermal energy.

To keep from overheating, the cyclist must get rid of the excess thermal energy generated in his body. If he cycles at this rate for 2 hours, how many liters of water must he perspire, to the nearest 0.1 liter?

A. 0.4 L

B. 0.9 L

C. 1.1 L

D. 1.4 L