Occasionally,
a collision will conserve kinetic energy:
in other words, it will be **elastic**.
Figuring out the properties of an elastic
collision can be pretty easy.

In two dimensions, the total vector momentum is still conserved. That means that each component of momentum remains the same before and after the encounter. The technique for using momentum to solve the properties of a collision takes a little more paper ....

When several objects collide or a single object explodes,
the individual pieces may fly all over the place.
However, if one considers all the pieces as a whole,
via the total mass and motion of the **center of mass**,
then Newton's Laws are simple and easy to solve again.

- Common sense and "center of mass"
- How to define the center of mass for a set of little balls
- The connection between the center of mass and momentum in a collision

Copyright © Michael Richmond. This work is licensed under a Creative Commons License.