Question

A car and a truck are moving with same kinetic energy. To stop them brakes exerting equal force are applied simultaneously. Then, which of the following statement is correct?

(a) The truck stops earlier as it covers less distance

(b) The car stops earlier as it covers less distance

(c) The car and the truck stop simultaneously covering equal distances

(d) The car stops earlier though it covers the same distance as the truck before coming to stop

Answer 1

Correct Option (d) The car stops earlier though it covers the same distance as the truck before coming to stop

Explanation:

As energy E is the same, car will have lesser momentum than the truck. Final momentum is zero for both. Hence, the change in momentum is less for the car.

Now, change in momentum = Impulse = F x t

Since, the force F is the same, it is clear that the car stops earlier.

Again, E = F x s

where, s is the distance travelled before coming to rest. This is the same  for both the car and the truck as E and F are same.