Question

A ball with a mass of `4 kg` and velocity of `4 m/s` collides with a second ball with a mass of `5 kg` and velocity of `- 7 m/s`. If `20%` of the kinetic energy is lost, what are the final velocities of the balls?

Answer 1

Already answered here: https://socratic.org/questions/a-ball-with-a-mass-of-4-kg-and-velocity-of-2-m-s-collides-with-a-second-ball-wit#504235