Rayat Shikshan Sanstha Satara New English School Dorlewadi
- Slides: 6
Rayat Shikshan Sanstha, Satara New English School Dorlewadi Smt. Gawade N. N. B. Sc. B. Ed. Std-9 th Sub-Science and Technology
12 THE PULL OF THE EARTH • • • Gravitation Law of gravitation Force of gravition of the earth(earth’s gravity) Acceleration Due to gravity Mass and Weight of an object
Gravitation • Centripetal force: When a body performs uniform circular motion, the net force responsible for it is directed to wards the centre of the circle. It is called centripetal force. • Gravitational force: There exists a force of attraction between any two particles of matter in the universe such that the force depends only on the masses of the particles and the gravitational forces and the mutual attraction is called gravitation.
Newton’s law of gravitation • Every object in the universe attracts every other object with a force which is directed proportional to the product of their masses and inversely proportional to the square of the distance between their centers. It acts along the line joining the centers. If two objects of masses m 1 and m 2 have their centers separated by a distance r, the gravitational force of attraction between the objects has magnitude F=G. m 1 m 2 / r 2 , where G is the universal constant of gravitation. • Importance of universal constant of gravitation • The motion of the moon around the earth. • The motion of the planets around the sun. • Thetides of the sea due to the moon and the sun.
Earth’s gravity The gravitational force exerted on a body by the earth’s gravity or simply the force of gravity. If r denoted the distance between the body and the center of the earth [r=R ( radius of the earth)], the gravitational force on the body due to the earth is F=G. m. M / r 2, where m is the masses of the body M is the mass of the earth • If h is the altitude at which the body is located , r=R+h. • F=Gm. M/(R+h)2 AND F =G. m. M / R 2 FOR h=0 •
Solved Example • 12. 3 force of gravition of the earth (earth’s gravity) • Let us find the gravition force between two boys sitting very close to each other. Let the mass of one • Boy be 40 kg. And the other 50 kg. Let the distance between them 0. 5 m. consider to be point masses. • we have, F = G m 1 m 2 • r 2 • Here r = 0. 5 m, m 1 = 40 kg m 2 = 50 kg • G= 6. 67 x 10 -11 • F = G m 1 m 2 • r 2 • = 6. 67 x 10 -11 x 40 x 50 • 0. 5 x 0. 5 • =5. 336 x 10 -9 N
