Two identical billiard balls collide head-on on a smooth horizontal table

PHYSICS · Single correct · AP · Physics 1: Algebra-based · Linear Momentum · Linear Momentum

Problem

Two identical billiard balls collide head-on on a smooth horizontal table. Ball 1 is moving at 3 m s−13\,\text{m\,s}^{-1} towards stationary Ball 2. After the perfectly elastic collision, which statement correctly describes their motions? (a) Both balls move off together at 1.5 m s−11.5\,\text{m\,s}^{-1} each in the original direction of Ball 1. (b) Ball 1 rebounds backward at 3 m s−13\,\text{m\,s}^{-1} while Ball 2 moves forward at 3 m s−13\,\text{m\,s}^{-1}. (c) They exchange their velocities; Ball 1 comes to rest and Ball 2 moves at 3 m s−13\,\text{m\,s}^{-1}. (d) Ball 1 continues at 3 m s−13\,\text{m\,s}^{-1} and Ball 2 remains at rest.

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