A car's engine is 20% efficient. When cruising, the car encounters an average retarding force of 1000 N. If the energy content of gasoline is 40 megajoules per liter, how many kilometers per liter does
The car get?

Question

Quizplus · Accepted Answer

The car's engine efficiency is 20%, meaning only 20% of the energy from gasoline is used for work. The work done against the retarding force is force times distance. With 40 MJ/L of energy in gasoline, only 8 MJ/L is used for work (20% of 40 MJ). The distance per liter is 8,000,000 J divided by 1,000 N, which equals 8,000 meters or 8 kilometers.

A Car's Engine Is 20% Efficient