^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 ".