Question

QA completely inelastic collision is one in which the two colliding particles-
A. Are separated after the collision.
B. Remain together after the collision.
C. Splits into two small fragments flying in all directions.
D. None of the above.

Answer 1

Hint: Recall the concept of coefficient of restitution in the collision. In a perfectly elastic collision, the energy and momentum are both conserved while in a perfectly inelastic collision, the momentum conserved but kinetic energy does not conserve.

Complete step by step answer:
To answer this question, we need to discuss all types of collisions.

- Elastic collision:
In elastic collisions, the kinetic energy and momentum of the colliding particles remains conserved before and after the collision. In the perfectly elastic collision, after the collision, the colliding particle bounces back to its original position.
Coefficient of restitution is the tendency of the body to come to its original position after the collision with the second body. Its value lies with 0 to 1. The coefficient of restitution is 1 for a perfectly elastic collision that represents the colliding particle returns to its original position.

- Inelastic collision:
In inelastic collisions, the kinetic energy of the body does not remain conserved after the collision. In partially inelastic collisions, some of the kinetic energy is lost during the collision and the coefficient of restitution lies close to 1. Therefore, the colliding particle does not return to its original position and also does not merge together.
In the completely inelastic collision, the huge portion of kinetic energy is lost during the collision and the coefficient of restitution is exactly equal to 1. This represents the colliding particle that is merged with the second particle.
Therefore, in inelastic collisions, two colliding particles remain together.

So, the correct answer is “Option B”.

Note:
Coefficient of restitution represents the loss in kinetic energy of the colliding body. For perfectly elastic collision, the coefficient of restitution is 0 which implies that the kinetic energy is totally conserved in the collision. In a perfectly inelastic collision, the coefficient of restitution is 1 which implies that the kinetic energy is totally lost in the collision.