1. Chapter 12: Forces and Motion
Section 12.3
Newton’s Third Law of Motion and Momentum

2. Newton’s Third Law of Motion
States that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.

3. Action and Reaction Forces
These forces that are produced by the two objects are action and reaction forces.
Sometimes action and reaction forces result in motion – sometimes they don’t.
Action and reaction forces do NOT cancel themselves out.

4. Momentum Product of an object’s mass and its velocity
An object at rest has a momentum of 0.
Momentum = Mass x Velocity
Measured in kilogram-meters/second
p = mv

5. Conservation of Momentum
Momentum is conserved in a closed system.
A closed system of objects means that there are no outside forces or objects acting on the objects in the system.
In a closed system, the loss of momentum by one object equals the gain of momentum by the second object.