Keeping Your CoolA 68 kg cyclist is pedaling down the road

Chapter , Problem 6P

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Problem 6P

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.

If the cyclist reaches his 15 km/h cruising speed by rolling down a hill, what is the approximate height of the hill?

A. 22 m

B. 11 m

C. 2 m

D. 1 m