Keeping Your Cool A 65kg cyclist is pedaling down the road at 12km/h , using a t

Question

Keeping Your Cool A 65kg cyclist is pedaling down the road at 12km/h , using a total metabolic power of 480W . 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 12km/h cruising speed by rolling down a hill, what is the approximate height of the hill?


As he cycles at a constant speed on level ground, at what rate is chemical energy being converted to thermal energy in his body, assuming a typical efficiency of 25% for the conversion of chemical energy to the mechanical energy of motion?

Explanation / Answer

1)Conserving mechanical energy of cyclist,

0.5mv2=mgh

h=0.5v2/g=0.567m

b)Thermal Power=0.75*Total metabolic rate=0.75*480=360W

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