Question

In an elastic collision of two billiard balls, which of the following quantities remain conserved the short time of collision of the balls (i.e., when they are in contact).

(a) Kinetic energy.

(b) Total linear momentum?

Given reason for your answer in each case.

Answer 1

(b) Total linear momentum remain conserved. While balls are in contact, there may be deformation which mean elastic potential energy which came from part of KE. Momentum is always conserved.