A ball collides with a second ball at rest. As a result of the collision, the first ball comes to rest and the second ball moves off at the speed of the first ball. In this collision
A) not enough information to say whether masses are equal or total kinetic energy is conserved.
B) the masses are unequal and total kinetic energy is not conserved.
C) the masses are unequal and total kinetic energy is conserved.
D) the masses are equal and total kinetic energy is not conserved.
E) the masses are equal and total kinetic energy is conserved.

Question

Quizplus · Accepted Answer

This is an example of an elastic collision between two objects, where both momentum and kinetic energy are conserved. Since the first ball comes to rest, its final kinetic energy is zero. The second ball, initially at rest, acquires the entire initial kinetic energy of the first ball, which means that the total kinetic energy of the system is conserved. Since kinetic energy is a scalar quantity, it does not matter whether the masses of the balls are equal or not. Therefore, the best choice is E, where the masses are equal and total kinetic energy is conserved.

A Ball Collides with a Second Ball at Rest