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Published byMargaret Stevens Modified over 9 years ago
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Newton’s laws and periodic motion
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Objects at rest tend to stay at rest, while objects in motion tend to stay in motion, unless acted on by an outside force Also called the Law of Inertia
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http://www.youtube.com/watch?v=yfeiD1nq- v4
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A car traveling 12 mph crashes into a wall. The driver is injured because of Newton’s 1 st law Seat belts and air bags seek to counteract Newton’s 1 st law It takes energy to get out of a chair because of Newton’s 1 st law
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The tendency to resist change
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If object are in equilibrium, usually there is no motion. Objects traveling at constant speed also exhibit equilibrium, though. Why?
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Objects travel in straight line unless acted on by an outside force The force required to move an object depends on the object’s mass and the acceleration Associate the 2 nd law with F = ma (or F = mg)
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For every action force there is an equal and opposite reaction force Think of pushes and pulls
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Describes motion where an object moves, and then returns to it’s starting point
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Apparent weight – the force exerted by a scale the object Example : an elevator accelerating up or down would change your apparent weight how? Weightlessness is when apparent weight is 0 You still have mass, there is no contact force pushing on the scale, though.
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Static friction force – the force exerted by 1 object on another when there is no movement between the two objects A book resting on the table
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Kinetic friction force - the force exerted by one object on another when there is motion between the two Example: a car’s tires and the road while the car is moving The force between a hockey puck and the ice as it slides across the rink
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Terminal velocity – when air resistance equals the pull of gravity The object is falling, but is not accelerating any more
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Air drag (resistance) – the force exerted on objects moving thru the air
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