# Collision of Billiard Balls#

In a game of billards, a red billiard ball is traveling in the positive x-direction with speed $$v$$ and the cue ball is traveling in the negative x-direction with speed $$3v$$. The two balls collide head on and the collision is elastic. The two balls have the same mass.

## Part 1#

Which statement concerning the velocities of the balls after the collision is true?

• red ball: $$-v$$, cue ball: $$3v$$

• red ball: $$v$$; cue ball: $$2v$$

• red ball: $$-3v$$; cue ball: $$v$$

• red ball: $$v$$; cue ball: $$3v$$