Suppose that a typical automobile engine operates at an efficiency of 25%. One gallon of gasoline releases approximately 150 MJ of heat when it is burned. (A megajoule, MJ, is a million joules.)
a. Of the energy available in a gallon of gas, how much energy can be used to do useful work in moving the automobile and running its accessories?
b. How much heat per gallon is released to the environment in the exhaust gases and via the radiator?
c. If the car is moving at constant speed, how is the work output of the engine used?
d. Would you expect the efficiency of the engine to be greater on a very hot day or on a cold day? Explain. (There may be competing effects at work.)