Conservation of Momentum Using Pasco Dynamics Cart

The Pasco dynamics carts are an attractive option to the air track for many basic mechanics demonstrations. The equipment takes up less space and makes less noise. The small amount of friction makes it easier to keep target carts stationary before collisions. Mass carts are each 0.5 kg and mass can be added in 0.5 kg increments. The end bumpers can be oriented for either elastic (magnetic repulsion) or inelastic (Velcro) collisions.

1. Two carts of equal mass are placed end to end, equidistant from two end bumpers set for inelastic collision. One cart has a cocked spring plunger. The plunger is triggered. The carts fly apart and stick to the end bumpers with simultaneous thumps. Using distances traveled in equal times as indicators of speed, it can be argued that positive and negative momenta are equal.
2. The mass of one cart is increased to 1.0 kg, with the other cart unchanged. The carts are placed on the track so that the 0.5 kg cart has twice the distance to a bumper that the 1.0 kg cart has. The plunger is triggered. Carts stick to bumpers simultaneously.