Heat engines take input energy in the form of heat, use some of that energy to do work, and exhaust the remainder. Similarly, a person can be viewed as a heat engine that takes an input of internal energy, uses some of it to do work, and gives off the rest as heat. Suppose that a trained athlete can function as a heat engine with an efficiency of 0.10.

(a) What is the magnitude of the internal energy that the athlete uses in order to do 4.85 104 J of work?

J

(b) Determine the magnitude of the heat the athlete gives off.

J