Chap9_Gravity

# 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
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)
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.
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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