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