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Learn about Newton's groundbreaking law of gravitation, which explains how objects attract each other based on mass and distance. Discover its implications on planetary orbits and gravitational forces.
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Isaac Newton • 1666, England (45 years after Kepler).
Questions • If the planets are orbiting the sun , what force is keeping them in orbit? • What force keeps the moon in its orbit? • Could the force of gravity be universal?
Newton’s Law of Universal Gravitation • Any two objects attract each other with a gravitational force, proportional to the product of their masses and inversely proportional to the square of the distance between them. • The force acts in the direction of the line connecting the centers of the masses.
Newton’s Law of Universal Gravitation http://scienceblogs.com/startswithabang/upload/2009/07/meet_our_second_moon/400px-NewtonsLawOfUniversalGravitation.svg.png
Henry Cavendish’sexperiment determined the proportionality constant G in 1798. http://www.newscientist.com/data/images/archive/1639/16390101.jpg
The Value of G. G= 6.67 x 10-11 N m2 / kg2
Change of Gravitational Force with Distance • Law of universal gravitation is known as an inverse square law.
Problem 1 • Two spheres of mass 35kg are 60m apart. • What force does one exert on the other? • If the mass of on is tripled and the radius is quadrupled how does the force change?
Problem 2 • Two spheres of equal mass have a force of gravity of 7x10-9 exerted on each other. If the distance between them is 7m, find the mass.
Problem 3 • Find the value of the gravitational acceleration g. The mass of the earth is 6.0 x 1024kg.