A driver spots a barricade ahead while his car is moving at
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A driver spots a barricade ahead while his car is moving at 54km h−1. The driver’s reaction time (the interval between noticing the barricade and pressing the brake pedal) is 0.50s. After the brakes are applied, the car experiences a uniform retardation of 5.0m s−2. The barricade is 45m away from the car at the instant it is first noticed.
(i) Compute the distance travelled by the car during the driver’s reaction time.
(ii) Determine the additional distance required to bring the car to rest once the brakes start acting.
(iii) State, with justification based on your calculations, whether the car stops before reaching the barricade. If it does stop in time, find the distance between the front of the car and the barricade when the car comes to rest.