A person can generate about 300 W of power on a treadmill If

A person can generate about 300 W of power on a treadmill. If the treadmill is inclined at 3% and a 70-kg man runs at 5 m/s for 27 min, consider the following. (a) Calculate the percentage of the power output that goes into heating up his body. Calculate the percentage that keeps him moving on the treadmill. (b) How much water would that heat evaporate? Assume the water starts at body temperature, 37 °C.

Solution

The energy used by the man in running for 27 minutes on inclined plane is mgX 5X(3/100)X(27X60)

Energy used by him per second= 70X9.81X5X(3/100) Joule/sec=103.005 Watts

Percentage of power out going in to heating up of his body= (103.005/300)X100=34.334%

Percentage of power that keeps him moving on treadmill = 65.665%

(b) total energy used in heating him up==103.005X27X60=166860 Joules=40837 cal

Suppose M kg of water is evaporated by this heat.

Then MXsX(100-37) = 1000XMX 63=40837

which gives M=0.648 kg