1. Conservation of Momentum
pbefore=pafter

2. Definition
Within a closed system (a system that does not exchange energy with the outside environment) momentum is always conserved.
Momentum can neither be gained or lost within a closed system.

3. Dump Truck and Bicycle
If a bicyclist traveling at maximum speed runs into a stationary dump truck, what happens?
If a dump truck moving at 5 m/s runs into a stationary bicyclist, what happens?
If a dump truck moving at 30 m/s runs head-on into a bicyclist at maximum speed, what happens?

4. Equal Mass
If two objects with equal mass, traveling at the same speed, get into a head-on collision, what happens?

5. Low Friction Push
A child and her father are standing still in the center of an ice rink. If the child tries to push her father, what will happen?
Demo

6. Collisions
In the collision of any two objects, the added momentum of both objects has to be the same before and after the collision

7. Three Types of Collisions
Elastic
Two objects collide and bounce off of each other with no deformation
Inelastic
Two objects collide with each other, crumple and deform, and sometimes stick together
Explosion
When one object becomes two or more objects
In a conventional explosion, one object breaks into many pieces that fly in all directions