Question

A cue ball with a mass of 0.170kg is moving at a speed of 15.0m/s toward the 5-ball (which has a slightly lower mass of 0.160kg) that is at rest. If the balls hit and bounce apart with the cue ball coming to a complete stop, what is the new speed of the 5-ball?

Answer 1

Final speed of the ball = 15.9375 m/s

Step-by-step explanation:

We can apply momentum conservation in the direction of motion of the two balls.

According to law of conservation of momentum, the sum of momentum of the two balls before and after the impact remains conserved.

Momentum = mass
`*` speed

Initial momentum = 0.17
`*` 15

= 2.55 kg m/s

But after the collision, the cue ball comes to rest. So there's only momentum for the second ball.

Final momentum = 0.16
`*` v = 2.55

v = 15.9375 m/s

This is the final speed of the second ball.