A 0.240 kg billiard ball moving at 3.00 m/s strikes a bumper and bounces straight back at 2.40 m/s, which is 80 percent of its original speed. What percentage of the ball's original kinetic energy remains after the bounce?

1. Kinetic energy depends on the square of speed, so it scales as the square of the speed ratio. 2. The final speed is 80 percent of the original speed, so the speed ratio is 0.80. 3. Squaring 0.80 gives 0.64, meaning 64 percent of the original kinetic energy remains. 4. 80 percent would be the case only if kinetic energy scaled directly with speed rather than its square. 5. 36 percent would be the energy lost rather than the energy remaining, since 100 percent minus 64 percent is 36 percent. _Source: OpenStax College Physics (CC BY 4.0), Ch 8 "Linear Momentum and Collisions", section 8.5 Inelastic Collisions in One Dimension_