How is that when: A wagon collides with the velocity (v) with another wagon (at rest, v=0) of the same mass (m) on a horizontal track, and when they collide they are connected together (think of wagons), that the velocity of the two objects are after the collision v/2? And now I exclude everything that has to do with friction (because in this text I just have written there was nothing said about friction). I hope you understand my question. And no, this ain't homework, I recently read it in a text but could never figure out how this was true. Thanks in Advance!