In an elastic collision of two billiard balls, which of the following quantities remain conserved during the short time of collision of the balls (i.e., when they are in contact).
(a) Kinetic energy . (b) Total linear momentum ?
Give reason for your answer in each case.

Explanation

In such a collision, total linear momentum is always conserved. However, when the balls are in contact, there may occur some deformation. So part of K.E. may be converted into elastic potential energy. Therefore, K.E. may not be conserved.