Collisions between objects – whether locomotives, shopping carts, or your foot and the sidewalk – can be complicated. Yet even in the most chaotic of collisions, as long as there are no external forces acting on the colliding objects, one principle always holds and provides an excellent tool for understanding the dynamics of the collision. That principle is called the Law of Conservation of Momentum.
After studying momentum and its conservation, juniors in Physics Honors conducted an experiment by colliding two cars. In this experiment, the students generated graphs comparing the velocity before and after the collision, and proved mathematically that momentum was conserved for the colliding cars.