a. What is Newton's first law of motion? c. What is Newton's second law of motion? b. What is Newton's third law of motion?

Sir Isaac Newton fundamentally changed our understanding of the universe with his three laws of motion, first published in 1687. The first law, the law of inertia, correctly states that an object's motion will not change unless an outside force interferes. This is why a hockey (Deals) puck can glide across the ice in a straight line until friction or a hockey stick stops it, and why you feel pressed into your seat when a car suddenly accelerates. The object (you) wants to remain at rest, but the car (the outside force) is moving you forward.

Newton's second and third laws quantify these interactions. The second law provides its famous equation, F=MA, which means the force required to move an object is directly related to its mass and the desired acceleration. This is intuitively correct; it takes much more effort to push a heavy truck than a small car. The third law explains that forces always come in pairs. The statement that every action has an equal and opposite reaction is demonstrated perfectly by a rocket launch. The rocket pushes hot gas down (the action), and the gas pushes the rocket up with an equal force (the reaction), propelling it into space.