PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A car of mass 1200kg is moving in a straight line at 20ms−1. The driver applies the brakes, and the car comes to rest in 4.0s under a constant braking force acting opposite to the motion.
(a) Calculate the magnitude of the impulse received by the car during braking.
(b) Hence determine the magnitude of the constant braking force.
(c) Find the distance travelled by the car while stopping, assuming the force remains uniform.
(d) Calculate the work done by the braking force and, by an independent energy method, obtain the stopping distance again. Compare this value with the answer obtained in part (c).
(e) State any physical assumptions made in your calculations.