Th e resistance to motion of an automobile consists of rolling resistance and aerodynamic drag. Th e weight of an automobile is 3000 lbf, and it has a frontal area of 20 ft2 . Th e drag coeffi cient...

Th e resistance to motion of an automobile consists of rolling resistance and aerodynamic drag. Th e weight of an automobile is 3000 lbf, and it has a frontal area of 20 ft2 . Th e drag coeffi cient is 0.30, and the coeffi cient of rolling friction is 0.02. Determine the percentage savings in gas mileage that one achieves when one drives at 55 mph instead of 65 mph on a level road. Assume an air temperature of 60°F.