Question

In an elastic collision of two billiard balls, the total kinetic energy is conserved ___________

(a) Completely

(b) For a short duration

(c) For a long duration but not completely

(d) Never

The question was posed to me in exam.

Asked question is from Coefficient of Restitution topic in chapter Gravitation of Engineering Physics I

Answer 1

The correct answer is (b) For a short duration

Explanation: During the short time of collision when the balls are in contact, the kinetic energy of the balls gets converted into the potential energy. In an elastic collision, though the kinetic energy before the collision is equal to the kinetic energy after the collision but kinetic energy is not conserved during the short time of collision.