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History of Laws of Motion. Aristotle ~ 350 B.C. He believed that the natural state for all objects was at rest. He believed all motion was caused by a force. If the force stopped, the object would eventually stop. Aristotle was WRONG!!!. Many people still think along the lines of Aristotle.
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Aristotle ~ 350 B.C. • He believed that the natural state for all objects was at rest. • He believed all motion was caused by a force. If the force stopped, the object would eventually stop.
Aristotle was WRONG!!! • Many people still think along the lines of Aristotle. • Objects do not “want” to be at rest. • If we can remove friction, objects will not stop. • On Earth, a completely frictionless surface is impossible.
Galileo ~ 1600 • Galileo argued that a moving object would move forever, without friction. • He also argued that objects naturally resist CHANGE in motion. • He called this inertia.
Inertia • Inertia — an object’s resistance to change in motion. • NOT just an object’s resistance to stopping, but also to slowing down and speeding up. • Inertia is measured by its mass. • The more mass, the more an object will resist a change in motion.
Sir Isaac Newton 1642-1727 • Developed and explained three laws to explain how objects move. • He also explained other concepts including gravity and calculus.
Newton’s First Law of Motion • An object at rest tends to stay at rest, and an object in motion tends to stay in motion in a straight line at a constant speed unless it is acted on by a net outside force. • An object is going to keep on doing what it is already doing unless something comes along and pushes it.
Examples • How can a magician pull a tablecloth out from under a stack of plates? • The plates have inertia; they will not move unless a force is applied to them. • Why do you need to wear a seatbelt? • You have inertia. When moving, you will continue moving at the same speed until an outside force stops you.
