Answer
See answers.
Work Step by Step
a. Find the work done per second from the information about the engine.
$$\frac{W}{t}=(180\frac{J}{cycle \cdot cylinder})(4\;cylinders)(25\frac{cycles}{s})=1.8\times10^4 J/s$$
b. The efficiency is given by equation 15–4a.
$$e=\frac{W}{Q_H}$$
Find the heat input per second.
$$Q_H=\frac{W}{e}$$
$$Q_H/t=\frac{W/t}{e}=\frac{1.8\times10^4 J/s }{0.22}=8.2\times10^4 J/s $$
c. To find out how long a gallon lasts, divide the energy contained in a gallon of gasoline by the rate at which the energy is being used.
$$\frac{130\times10^6 J}{8.182\times10^4 J/s }=1589s\approx 26\;min$$