Question

A 1242 kg car is moving at 22.5 m/s when it skids to a stop. The car's brakes, which caused the stop, applied a force of -7210 N in order to slow down the car. What was the acceleration of the car during it's slowing down to rest?

Answer 1

The work needed to stop the car is

W = ∆K = 0 - 1/2 (1242 kg) (22.5 m/s)² ≈ -314 kJ

A stopping force that does this amount of work, pointing in the opposite direction with magnitude 7210 N, would be exerted over a distance x such that

W = (-7210 N) x   ==>   x ≈ 43.6 m