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Gravitation has been the most common phenomenon in our lives but somewhere down the line we don't know musch about it. So here is a presentation whic will help you out to know what it is !! I'll be makin it available for download once i submit it in school :P :P ! Coz last one of the brats showed the same presentation that i uploade and unfortunatele his roll number fell before mine ! I was damned..:D :D :P

- 1. GRAVITATION Gravity is matter's memory it once was light.
- 2. • Gravitation, the attractive force existing between any two particles of matter. • It was Sir Isaac Newton who not only provided this explanation in his famous inverse square law of gravitation, but managed to "synthesize" the explanation of motion on earth and motion in the heavens. This had profound philosophical and scientific consequences. What Gravitation is??
- 3. • The unification into what became the laws of gravitation became a symbol of the predictive and quantitative power of science. The fact that a single law could explain the motion of a cannonball and the motion of Mars revolutionized our understanding of our place in the universe.
- 4. • Kepler’s First Law (Law of Orbits): Each planet moves in an elliptical orbit with the Sun at one focus. KEPLER’S LAWS
- 5. • Kepler’s Second Law (Law of Areas): The speed of planet varies in such a way that the radius vector drawn from the
- 6. • Sun to a planet sweeps out equal areas in equal times. Thus the law states that the areal velocity of the planet is constant. • Areas; A1, A2 and A3 are swept by the radius vector in equal times. So, according to Kepler’s second law, A1 = A2 = A3
- 7. • Also, the planet covers unequal distances S1, S2 and S3 in equal times due to the variable speed of the planet. Maximum distance is covered in a given time when planet is closest to the Sun. When the planet is closest from the sun, its velocity and the kinetic energy of the planet is maximum.
- 8. • When the planet is farthest from the Sun, its velocity and the kinetic energy is minimum. However, the total energy of the planet remains constant.
- 9. • Kepler’s Third Law (Law of Periods)- The square of the period of revolution of a planet around the Sun is proportional to the cube of the semi-major axis of its elliptical orbit. AB is the major axis and CD is the minor axis. AO or OB is called semi-major axis. • Let, T = Period of revolution of planet around Sun. R = length of semi- major axis According to Kepler’s third law, T2 ∝ R3 or T2 = KR3
- 10. • Let T1 and T2 be the periods of any two planets around the Sun. Let , R1 and R2 be the lengths of their respective semi – major axes Then,
- 11. • Every particle of matter in the universe attracts every other particle with a • force which is directly proportional to the product of their masses and • inversely proportional to the square of the distance between them. UNIVERSAL LAW OF GRAVITATION
- 13. • The force of attraction between any two particles in the universe is known as force of gravitation. • The force of gravitational attraction between the two bodies acts along the line joining their center. This force is mutual and Characteristics of gravitational force
- 14. • Combining these factors we get & • {Where the value of G in SI units is (6.67 × 10– 11 Nm2 kg–2). The universal gravitational constant (G) is numerically equal to the force of attraction between two bodies, each of unit mass, separated by unit distance.
- 15. • In vector notation, Newton’s law of gravitation is written as follows:
- 16. • Let us consider a body of mass m lying on the surface of the Earth of mass M and radius R. Let g be the value of acceleration due to gravity on the free surface of Earth. ACCELERATION DUE TO GRAVITY OF THE EARTH
- 17. • • Since the value of g at a given place on the Earth is constant and R is also constant Therefore • Thus, the value of acceleration due to gravity decreases with increase in height above the surface of Earth. Variation of g with Altitude (Height)
- 18. • We know that, • ∴ Loss of Weight at Height h(<<R)
- 19. • Assume the Earth to be a homogeneous sphere (having uniform density) of radius R and mass M. If at a depth h, the gravity will be gh. Then, the difference is given by Variation of g with Depth
- 20. • Here g- gh gives the decrease in the value of g. • Since g is constant at a given place of the Earth and R is also a constant, ∴
- 21. Thus the value of acceleration due to gravity decreases with the increase of depth.
- 22. • The force of gravity is a conservative force and we can calculate the potential energy of a body arising out of this force, called the gravitational potential energy. GRAVITATIONAL POTENTIAL ENERGY
- 23. • This work done is equal to the gravitational potential energy U of mass m.
- 24. • According to convention, the gravitational potential energy at the surface of the Earth is taken to be zero. ∴ U = m x g x h
- 25. • A satellite is a body which is continuously revolving around a bigger body. Satellite may be regarded as a ‘secondary body’. • The centripetal force required by a satellite to move in a circular orbit is provided by the gravitational force of attraction between the satellite and the body around which it revolves. SATELLITES
- 26. • Planets can be said to be the natural satellites of the sun. • Moon is a natural satellite of the Earth which revolves around the Earth in a nearly circular orbit of radius • 3.85 x 105 km and completes one revolution is 27.3 days.
- 27. • GEOSTATIONARY SATELLITES • POLAR SATELLITES TYPES OF SATELLITES
- 28. • A geosynchronous satellite is a satellite in geosynchronous orbit, with an orbital period the same as the Earth's rotation period. Such a satellite returns to the same position in the sky after each sidereal day. GEOSTATIONARY SATELLITES
- 29. • These satellites have revolutionized global communications, television broadcasting and weather forecasting, and have a number of important defense and intelligence applications. USES
- 30. • Polar satellite is a satellite that revolves around the Earth in a polar orbit. It is usually as close as ≈ 250km. • As the Earth rotates about its axis a polar satellite passes many different places during its motion unlike the geostationary satellite. POLAR SATELLITES
- 31. • Polar satellites are being used to record the land and sea temperatures, take pictures of cloud and predict the movement of winds and ultimately forecast the weather reporting. • It is hence also called a Monitoring or weather satellite. USES