PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A car of mass 1000kg is moving on a straight, horizontal road at 72kmh−1. The driver applies the brakes so that a constant opposing force of 2500N acts on the car until it comes to rest.
Answer the following questions in sequence:
(i) Derive an expression for the minimum distance travelled by the car before coming to rest in terms of its initial speed v0, its mass m and the magnitude of the constant braking force F. State the assumptions made.
(ii) Using your expression, calculate the minimum stopping distance for the given numerical data.
(iii) If the braking system is improved so that the magnitude of the opposing force can be doubled without locking the wheels, by what factor will the stopping distance change? Show your working clearly.