# Momentum - Bumping 2 carts with magnets

1. Apr 20, 2014

### Dethrone

Momentum -- Bumping 2 carts with magnets...

1. The problem statement, all variables and given/known data
I recently did an experiment in which I had bump a dynamic cart into another one with their magnets facing inwards to emulate a perfectly inelastic collision. Upon examining the initial and the final momentum of the cart, the final momentum was slightly less. Where did that fraction go, other than experimental error?

3. The attempt at a solution

My hypothesis is that there is friction acting upon the motion of the carts, so the velocity measured is less than it it should be, resulting in less momentum. Because momentum = mv. Also, because of the connection between kinetic energy and momentum. We know that kinetic energy is not conserved, so if a lot of the kinetic energy is lost as sound/heat energy, then the carts would have less kinetic energy than it would have in a perfect ideal situation. And less kinetic energy = less velocity = less momentum than it would have. So that's my hypothesis of why the final momentum is less than it's initial in terms of the calculations. But ofc, it's suppose to be conserved.

2. Apr 20, 2014

### haruspex

The loss of energy is not relevant, but certainly friction / rolling resistance could reduce the momentum since this is an external force.