College Physics with MasteringPhysics 7th Edition by Jerry Wilson,Anthony Buffa,Bo Lou

تمرين 50

A cyclist with a total skin area of 1.5 m 2 is riding a bicycle on a day when the air temperature is 20 °C and her skin temperature is 34 °C. The cyclist does work at about 200 W (moving the pedals) but her efficiency is only about 20% in terms of converting energy into mechanical work. Estimate the amount of water this cyclist must evaporate per hour (through perspiration) to get rid of the excess body heat she produces. Assume a skin emissivity of 0.70.