Momentum is a vector describing a "quantity of motion"
or in mathematical terms p (momentum) = mass (m) times velocity (v).
Conservation of Momentum
In a closed system, such as when two objects collide, the total momentum remains the same, though some may transfer from one object to the other. Momentum is always conserved in a closed system, but most sporting situations in the real world are not a closed system. For example, when a baseball bat hits the ball, the ball will be squished to a certain degree. After few milliseconds, it rebounds back. This contraction and rebound action is causes the release of heat energy, and some momentum is lost, or transferred elsewhere.
As momentum is the product of mass and the velocity, you can increase momentum by increase either of these elements. In sport, examples include using a heavier bat or racket and increasing running speed or hand speed.
Angular momentum is the product of Moment of Inertia and Angular Velocity. Moment of Inertia is the angular counterpart to mass - it is the measure of the resistance of an object to changing its angular speed.
A good example of angular momentum in action is with figure skaters. A figure skater starts a spin by pulling in his arms to lessen his Moment of Inertia. By the Conservation of Momentum Principles, the angular speed must then increase. To come out of the spin, a skater simply extends her arms to increase angular momentum and decrease angular velocity.
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