Chapter 11.2, Problem 26SSC

To determine

Whether kinetic energy is conserved or not during head on collision between glob of chewing gum and rubber ball.

Explanation of Solution

Introduction:

Momentum conservation: The duration of collision is very-very small therefore the effect of external force like gravitational force or friction force are not considered. The magnitude of average impulse acting on body during collision is much more than external force.

Impulsive force is a type of internal force. Thus, the total momentum of system is always conserved.

Energy conservation: During collision, the net energy of system is always conserved. It means that the sum

of total energy before the collision is always equal to the sum of total energy after collision. If the direction of motion of objects before and after collision is along the same straight line, then it is known as head on collision.

When rubber ball collides with glob of chewing gum at that time kinetic of the system is not conserved because there is a permanent deformation in size and shape of chewing gum.

Thus, there is permanent loss in the kinetic energy.