Newton's Laws of Motion/First Law

Physical Law
Newton's first law of motion is one of three physical laws that forms the basis for classical mechanics.

Statement of Law

 * Every body remains in a state of constant velocity unless it is acted upon by an external unbalanced force.

Also see

 * Newton's Second Law
 * Newton's Third Law

As he put it:
 * "A body remains at rest or, if already in motion, remains in uniform motion with constant speed in a straight line, unless it is acted on by an unbalanced external force."