Elastic and Inelastic Collisions

There have been two articles in this journal^1,2 that described a pair of collision carts used to demonstrate vividly the difference between elastic and inelastic collisions. One cart had a series of washers that were mounted rigidly on a rigid wooden framework, the other had washers mounted on rubber bands stretched across a framework. The rigidly mounted cart bounced off a wall with little loss of velocity; the rubber mounted version had very little recoil speed and came to a halt. For teachers who would like a faster way to demonstrate the effect with a less elaborate device demanding less skill to prepare, we describe a single cart with just one moving part and easily made, serving as a model that demonstrates the idea of both elastic and inelastic collisions. The finished product is shown in Fig. 1.