Unit 03 -- Interactions and Momentum

1. Interaction -- a more complete description of a push on an object. It includes the force that Object 1 applies to Object 2, and also the equally-sized force that Object 2 applies back on Object 1 in an opposite direction. It is important to remember that these two forces ALWAYS act on different objects.
2. Newton's Third Law -- to every force applied by one object on another object, there is an equal but opposite reaction force applied by the second back on the first.
3. Vector Components -- Any vector can be broken down into its purely horizontal and vertical parts to make it easier to use in vector addition.
4. Momentum -- inertia in motion. It is symbolized with a lowercase p and found by multiplying the mass and velocity of an object. It is measured in strange units: kg * m/s. It is a vector quantity.
5. Impulse -- a quantity that describes both the size of the average net force acting on an object and the time over which it acts. It is measured in N * s. It is symbolized by a capital J.
6. Impulse - Momentum Theorem -- states that the impulse acting on an object causes an equivalent change in momentum for that object.
7. System -- a collection of objects that can be analyzed as a whole.
8. Open System -- a collection of objects in which forces and energy are allowed both into and out of the collection, making analysis much more difficult.
9. Closed System -- a collection of objects in which forces and energy are (nearly completely) kept inside the system, without allowing forces or energy to come into the system. As a result, this type of system is much easier to analyze.
10. Law of Conservation of Momentum -- a rule of physics that states that vector sum of all the momentum vectors at one particular time in a closed system will be the same at any other particular time. It is used in the analyses of systems containing collisions and/or explosions. In all three -- elastic collisions, inelastic collisions and explosions -- the total system momentum is conserved.
11. Elastic Collision -- a collision in which objects rebound without any lasting deformation or the generation of heat.
12. Inelastic Collision -- a collision in which objects become distorted, generate heat and possible stick together.
13. Explosion -- an inelastic collision in reverse.

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