NEWTON'S LAWS

Newton's First Law - An object which is moving at a constant velocity or at a state of rest does not change its state unless a force acts upon it.

Newton's Second Law - Acceleration of an object increases as the amount of force causing the acceleration increases.

Newton's Third Law - Every force has an equal and opposite reaction.

Definitions from:

http://www.clas.ufl.edu/users/rhatch/NSF-PLANS/2-2_NEWTON.htm