Hi, this is related to another post I have about a billiard setup. This is a refactored version of the query. If u have the time please build this simple set up.. 1 box plane say 20:1:20 4 spherical bodies. Add Either rigid or physicbodies (depending on physics engine) For physic materials make the balls have a bounciness of between .92 and 1. Frictional forces can be anything any setting. Min, max etc. Set all 4 balls on x or z axis to be same so they make a straight line. Set ball 4 to be away from the other 3 balls which are radius to radius. But still all 4 make a straight line on either x or z axis. Give the separate ball an initial velocity to hit the first ball in the 3 ball series head on. This should cause a rebound of the projectile ball which is fine. The problem is: the 3 balls now move together.. This is not realistic. As in reality the 3 balls should roll at different velocities. In which the last of the 3 balls is fastest. Then the next which is slower and the collision ball the slowest thus increasing distance between them over time. Yet they all roll together and stay radius to radius.