What is the final velocity of the second billiard ball after an elastic collision?

Explanation:

Conservation of Momentum: Before the collision, the first billiard ball has a momentum of 12.39 kg∙m/s (2.1 kg * 5.9 m/s) due west. Since the collision is elastic and momentum is conserved, the total momentum before the collision is equal to the total momentum after the collision.

Initial momentum of the second ball: The second billiard ball is initially at rest, so its initial momentum is 0 kg∙m/s.

Final momentum of the second ball: After the collision, the second ball travels due west with a momentum of -12.39 kg∙m/s to ensure momentum conservation.

Calculating the final velocity: To find the final velocity of the second ball, we divide its momentum (-12.39 kg∙m/s) by its mass (2.1 kg) to get -5.90 m/s due west.

Therefore, the magnitude of the final velocity of the second billiard ball is 5.90 m/s due west, moving in the same direction as the first ball.