One model of tennis ball launcher has advertised that it is capable of imparting 14,000J of kinetic energy to a 0.4kg ball initially at rest. A student carefully measures the compression of the spring to be 0.15m. What is the spring constant for the spring?

Aball with a mass of 275 g is dropped from rest, hits the floor and rebounds upward. if the ball hits the floor with a speed of 2.40 m/s and rebounds with a speed of 1.70 m/s, determine the following. (a) magnitude of the change in the ball's momentum (let up be in the positive direction.)