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GRAVITATION 10th Grade Physics 10th - Physics

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INTRODUCTION Why is Moon going around the earth in a circular orbit? Why doesnt it fall down to the earth? Why doesnt it go away from earth? 10th - Physics

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Newton and the Apple Sir Isaac Newton got answers for all these questions, when he was sitting under an apple tree. He explained the answers for these questions as Universal law of gravitation 10th - Physics

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The law of Gravitation 10th - Physics What made that Apple fall to the ground ? Every object on the surface of the Earth is attracted towards the center of the Earth. This force is called as Gravitational force.

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The law of Gravitation 10th - Physics Every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them. This force acts along the line joining the two particles.

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The law of Gravitation where: F 1, F 2 are the force between the masses, G is the constant of proportionality m 1 is the first mass, m 2 is the second mass, and r is the distance between the centers of the masses. 10th - Physics G is called as the universal Gravitational constant. It has the same value for all the objects. Its accepted value is 6.67 x 10 -11 Nm 2 kg -2

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The law of Gravitation 10th - Physics

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Weight and Weightlessness 10th - Physics

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Weight and Weightlessness Astronauts experience Weightlessness when their space craft orbits around the Earth. The gravitational pull is used in providing the necessary centripetal force to the space craft. Due to the centripetal force, there is no reaction on the occupant in a space craft. This condition of zero reaction is called Weightlessness., 10th - Physics The value of g at a distance of 3.84 x 10 5 km (distance of the moon), the value is found to be nearly 2.7 x 10 -3 ms -2

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Variation of g 10th - Physics

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Motion of planets around the Sun Johannes Kepler is best known for his discovery of the three laws of planetary motion. These laws are based on his observations and the data collected by Tyco Brahe. Keplers First Law: 10th - Physics The orbits of the planets are ellipses, with the Sun at one focus of the ellipse.

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Motion of planets around the Sun Keplers Second Law: 10th - Physics An imaginary line drawn from the sun to a planet, sweeps equal areas in equal intervals of time.

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Planets around the Sun Keplers Third Law: 10th - Physics

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Keplers third law can be used to find Mass of the sun Distance of a planet Period of revolution of a planet Newton showed that Keplers laws can be derived from the universal law of gravitation., 10th - Physics Planets around the Sun

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Importance of the law of Gravitation The law of gravitation successfully explained several phenomena: The force that binds us to the Earth The motion of moon around the Earth The motion of planets around the sun The tides due to the Moon and the Sun The law of gravitation successfully predicted The existence of planets beyond the Uranus Observations in the deviations in the orbit of Uranus led to the discovery of Neptune in the nineteenth century Smaller deviations in the orbit of Neptune led to the discovery of Pluto in 1930 Pluto though was initially considered as planet, now has been given the status of a dwarf planet, because of its size which is only twice of its Moon., 10th - Physics

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Exercise 1.State the universal law of Gravitation 2.What led Newton to develop the law of Gravitation? 3.Why is the law of gravitation called a universal law? 4.What is weight? 5.How does the acceleration due to gravity vary with height? Explain 6.Mention three points successfully explained by the law of Gravitation 7.What led to the discovery of the planet Neptune? 8.What led to the discovery of planet Pluto? 9.What is meant by Weightlessness? Explain with an example., 10th - Physics