In this video Newton’s Cradle meets a trolley, with some curious consequences:

Notice how, when the trolley-cradle hybrid hits the wall for the first time, the balls start swinging. The trolley appears to “row”, like a boat, up the track. Upon the 2nd collision something even stranger seems to happen.

To understand the mechanics of this, one would no doubt need to delve into the Euler-Lagrange equations… perhaps one for you to tackle in a few years time Paddy!