PHYSICS · Subjective · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A car is travelling along a straight road at 20m/s. The driver applies the brakes and the car comes to rest in 4s.
(a) Calculate the magnitude of the car’s retardation while the brakes are applied.
(b) Suppose the same magnitude of acceleration (but acting in the forward direction) had been applied to the car for 6s when it was initially at rest. Determine the speed the car would have reached.
(c) Compare the signs of the accelerations in parts (a) and (b) when the positive direction is taken as the original direction of motion. Explain your answer in one or two sentences.