Question

A lorry and a car with the same kinetic energy are brought to rest by the application of brakes which provides equal retarding forces. Which of them will come to rest in a shorter distance?
(A) Lorry
(B) Car
(C) Both will stop at the same distance
(D) Car stops first but takes longer distance

Answer 1

Hint :We know that kinetic energy is defined as the energy that is produced by an object due to its motion. When an object is set to acceleration, there is a definite need to apply certain forces and the energy transferred is referred to as kinetic energy. We know the relation between the force and change in kinetic energy i.e. $ K.E = \dfrac{1}{2}m{v^2} $

Complete Step By Step Answer:
As per the question that lorry and car are moving with the same kinetic energy. Here in the formula of the kinetic energy where $ m $ is the mass and $ v $ is the velocity.
Since both the vehicles have the same kinetic energy and are subject to the same force $ (F) $ , the distance covered by both lorry and car will be the same. Thus both will stop at the same distance.
Hence the answer is (c) Both will stop at the same distance.

Note :
We should note that both are brought to rest by the application of brakes which provides equal retarding forces. So both the lorry and car will travel the same distance before coming to rest and so both will travel the same distance before coming to rest. We should know that if there is a negative sign in the formula for force then it indicates that the applied force is retarding.