Newtons Law of Universal Gravitation Physics Mrs Coyle

Newton’s Law of Universal Gravitation Physics Mrs. Coyle

Isaac Newton n 1666, England (45 years after Kepler).

Questions n n n 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 n 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. n 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/400 px-Newtons. Law. Of. Universal. Gravitation. svg. png

Why does the moon not fall straight down onto the earth?

Henry Cavendish’s experiment determined the proportionality constant G in 1798. http: //www. newscientist. com/data/images/archive/16390101. jpg

The Value of G. G= 6. 67 x 10 -11 N m 2 / kg 2

Change of Gravitational Force with Distance n Law of universal gravitation is known as an inverse square law.

Problem 1 n Two spheres of mass 35 kg are 60 m apart. A) What force does one exert on the other? B) If the mass of on is tripled and the radius is quadrupled how does the force change?

Problem 2 n Two spheres of equal mass have a force of gravity of 7 x 10 -9 exerted on each other. If the distance between them is 7 m, find the mass.

Problem 3 n Find the value of the gravitational acceleration g. The mass of the earth is 6. 0 x 1024 kg.