Two identical billiard balls collide head-on on a smooth horizontal table. Ball 1 is moving at 3ms−1 towards stationary Ball 2. After the perfectly elastic collision, which statement correctly describes their motions?
a) Both balls move off together at 1.5ms−1 each in the original direction of Ball 1.
b) Ball 1 rebounds backward at 3ms−1 while Ball 2 moves forward at 3ms−1.
c) They exchange their velocities; Ball 1 comes to rest and Ball 2 moves at 3ms−1.
d) Ball 1 continues at 3ms−1 and Ball 2 remains at rest.