A 1000-kg car is driving toward the north along a straight road at a speed of 20.0 m/s. The driver applies the brakes and the car comes to a rest in a distance of 140 m. What is the constant force applied to the car to bring it to rest?

Question

Quizplus · Accepted Answer

The work-energy principle states that the work done by the brakes is equal to the change in kinetic energy. The initial kinetic energy is (1/2)mv² = (1/2)(1000 kg)(20 m/s)² = 200,000 J. The work done is force × distance, so force = work/distance = 200,000 J / 140 m = 1,428.57 N, approximately 1.43 × 10³ N south.

A 1000-Kg Car Is Driving Toward the North Along a Straight