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## Isaac Newton

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**Isaac Newton**• Initial calculations didn’t work**Isaac Newton**• Initial calculations didn’t work • Placed theory in a drawer for 20 years**Isaac Newton**• Initial calculations didn’t work • Placed theory in a drawer for 20 years • When the comet of 1670 came, Halley convinced him to re- look at it.**Isaac Newton**• Initial calculations didn’t work • Placed theory in a drawer for 20 years • When the comet of 1670 came, Halley convinced him to re- look at it. • Produced the Law of Universal Gravitation**Law of Universal Gravitation**F ~ m1m2 d2 F = G x m1m2 d2 G = 6.67 x10-11 N m2 / kg2**Universal gravitation constant**(G) = 6.67 x10-11 N m2 / kg2 • Equals the force of attraction between two 1kg masses 1 meter apart**Universal Law of Gravitation**• Youtube http://www.youtube.com/watch?v=NPyH93vXutk http://www.youtube.com/watch?v=D5BQkdyAw8A**Universal gravitation constant**• Philipp von Jolly’s – measurement experiment • Mercury Flask and a 6 ton lead ball**Gravitational Force**• The force is extremely small and for most tangible things it is two sensitive to measure • attraction to one another is not measurable but the attraction to the earth is what we call weight**Gravitational Force**• It is based on the distance to the center of the earth – • weigh less on a mountain • Is this a new diet infomercial???**Book Questions**• By how much does the gravitational force between two objects decrease when the distance between their centers is doubled, tripled, and increased tenfold? • Consider an apple that is at the top of a tree and is being pulled by the earths gravity with a force of 1 N. If the tree were twice as tall, would the force of gravity be only ¼ as strong?**Spring Tides**Higher Than Average tides and lower than average tides**Neap Tides**High tides lower than average and low tides higher than average