Chap9_Gravity - Here is how the formula is used Force G = G...

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Chapter 9 Gravity
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Newton and the Moon Newton realized that Earth’s gravity was the centripetal force that kept the moon in orbit. He understood that gravity got weaker at larger distances. Gravity force
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We don’t notice that gravity gets weaker as we move away from Earth because we rarely go very far. Moon is 30 Earth diameters away
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Universal Law of Gravity Force of gravity has magnitude given by Force G = G x Object A Object B Mass of Object A x Mass of Object B Distance x Distance DISTANCE Force Force Equal and opposite forces (Newton’s Third law)
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Inverse Square Law Gravity force weakens with distance as the inverse of the square of the distance. Earth Gravity 1/4 Earth Gravity Twice the Distance
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Universal Gravity Constant, G In the formula for gravity force, we have G = 0.0000000000667 N m 2 / kg 2 = 6.67 x 10 –11 N m 2 / kg 2 The formula and the constant are called “universal” because they apply anywhere in the universe.
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Application Find gravity force for a 1 kg mass on surface of Earth.
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Unformatted text preview: Here is how the formula is used: Force G = G x Mass of Object A x Mass of Object B Distance x Distance DISTANCE = Earth’s Radius Object B (Earth) Object A (1 kg mass) Force = ( 6.67 x 10 –11 ) x = 9.8 N ( 6.38 x 10 6 ) 2 Universal Gravity Constant, G Earth’s Radius Earth’s Mass Additional Question Find gravity’s acceleration on the 1 kg mass. Using Newton’s Second Law, Acceleration = = = 9.8 m/s 2 , which we’ve been rounding off as 10 m/s 2 . Force Mass 9.8 N 1 kg Weightlessness Earth is nearby In deep space, far away from all planets, stars , etc., there is almost no gravity force. In orbit near Earth, gravity is still strong (only 10% less than on surface). Why are spacecraft astronauts “weightless”? Check: Forces On the Ferris wheel, where do you feel heaviest? where do you feel lightest? This is similar to the elevator problem we did previously… E A B C D Velocity Centripetal Force...
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This note was uploaded on 04/29/2010 for the course PHYS 100 taught by Professor Nidhalguessoum during the Spring '10 term at American University of Sharjah.

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Chap9_Gravity - Here is how the formula is used Force G = G...

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