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Newton's First Law: "Every body travels in a straight line with constant speed unless acted on by a force"
Newton's Second Law: "The rate of change of a body's momentum is proportional to the force acting on it"
Newton's Third Law: "If body A exerts a force on body B, then body B exerts a force of equal magnitude and opposite direction on body A" or more commonly "For every action, there is an equal and opposite reaction"
Newton first gave his laws in the first volume of his Principia in 1687 and, using the mathematical tools of his newly developed calculus, proved many results concerning the motion of idealised particles. In the third volume, he showed how, combined with his law of gravity, his laws of motion explained the motion of the planets and the Laws of Kepler. Not until 1916 and Albert Einstein's theory of relativity did anyone improve upon Newton's model of the motions of the planets.