^Newton (1729) p. 19, Axioms or Laws of Motion . "Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impress'd thereon ".
^Newton (1729) p. 19, Axioms or Laws of Motion . "The alteration of motion is ever proportional to the motive force impress'd; and is made in the direction of the right line in which that force is impress'd ".
^Newton (1729) p. 20, Axioms or Laws of Motion . "To every Action there is always opposed an equal Reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts ".
^Newton (1729) p. 24, Axioms or Laws of Motion . "I was only willing to show by those examples the great extent and certainty of the third Law of motion.For if we estimate the action of the agent from its force and velocity conjunctly, and likewise the reaction of the impediment conjunctly from the velocities of its several parts,and from the forces of resistance arising from the attrition, cohesion, weight, and acceleration of those parts,the action and reaction in the use of all sorts of machines will be found always equal to one another. And so far as the action is propagated by the intervening instruments, and at last impressed upon the resisting body, the ultimate determination of the action will be always contrary to the determination of the reaction. "