When an automobile moves with constant velocity, the power developed in a certain engine is 76.8 hp. What total frictional force acts on the car at 51.7 mi/h?

2,480.2 N

Explanation:

power output = 76.8 hp = 76.8 x 746 (to convert from hp to Watts) = 57292.8 W

velocity = 51.7 mph = 51.7 x 0.44704 (to convert to m/s) = 23.1 m/s

find the frictional force acting on the car

power output = frictional force x velocity

frictional force = power output / velocity

frictional force = 57,292.8 / 23.1 = 2,480.2 N