Question

A ball with a mass of `4 kg` and velocity of `5 m/s` collides with a second ball with a mass of `9 kg` and velocity of `- 4 m/s`. If `40%` of the kinetic energy is lost, what are the final velocities of the balls?

Answer 1

This is a Conservation of Energy question

Explanation:

We know that `m_1v_1=m_2v_2`

We also know that the energy before the collision has to equal the energy after the collision. Use `KE_1=1/2m_1v_1^2` to find the initial KE. Then `KE_2=.6KE_1` and you can find the final velocities from there.