Momentum

Program Notes:

Every body perseveres in its state of being at rest or of moving uniformly straight forward except insofar as it is compelled to change its state by forces impressed. Every body under the sole action of its innate force moves uniformly in a straight line indefinitely unless something extraneous hinders it.

A change in motion is proportional to the motive force impressed and takes place along the straight line in which that force is impressed.

To every action there is always opposed an equal reaction: or the mutual actions of the two bodies upon each other are always equal, and directed to contrary parts.

— Sir Issac Newton