Question

A 7 kg ball of putty moving to the right has a head-on inelastic collision with a 1 kg putty ball moving to the left. If the combined blob doesn't move just after the collision, what can you conclude about the relative speeds of the balls before they collided?

Answer 1

Answer: The relative speed of the balls are equal.

Explanation:

For the bodies not to move after colliding, this means the velocities of the bodies before collision moving in opposite direction are the same as such the bodies will remain at rest after collision. For the bodies to move after collision, the bodies must have different velocities before collision.