# 1. State Newton's law of gravitation. Hence define universal gravitational constant . Give the value and dimensions of G. 2. Define acceleration due to gravity. Show that the value of 'g' decreases with altitude or height . 3. Discuss the variation of ‘g' with depth. What happens to 'g' at the centre of earth? 4. Write down the formula of gravitational potential energy and obtain from it an expression for gravitational potential . 5. What do you mean by gravitational potential energy of a body? Obtain an expression for it for a body of mass m lying at distance r from the centre of the earth . 6. Define the term orbital speed. Establish a relation for orbital speed of a satellite orbiting very close to the surface of the earth. Find the ratio of this orbital speed and escape speed. 7. What are geostationary satellites? Calculate the height of the orbit above the surface of the earth in which a satellite, if placed, will appear stationary. 8. State Kepler's law of planetary motion. 9. What is a polar satellite? Explain how does it scan the entire earth in its each revolution? Give two important uses of a polar. Satellite. 10. What do you mean by the term weightlessness? Explain the state of weightlessness of (i) a freely falling body (ii) an astronaut in a satellite orbiting the earth. 11. Obtain an expression for the acceleration due to gravity on the surface of the earth in terms of mass of the earth and its radius. Discuss the variation of acceleration due to gravity with altitude and depth. 12. State the conditions necessary for a satellite to appear stationary.

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1.Newton's law of gravitation states that every body in this universe attracts every other body with a force which is directly proportional to the product of their masses and is inversely proportional to the squares of the distance between them.
This force depends upon the masses of the bodies which attracts each other and the distance between them.
According to Newton' law of gravitation :
F =
Thus, universal gravitational constant is equal to the force of attraction acting between two bodies each of unit mass, whose centre are placed unit distance apart.
3. Variation of g with depth (d) is given by :
g' = g
â€‹where R is the radius of earth.
At centre of earth, d = R
Hence, at centre of earth, the value of acceleration due to gravity (g) is zero.

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1. (i) Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

(ii) The gravitational constant denoted by letter G, is an empirical physical constant involved in the calculation(s) of gravitational force between two bodies.

2. gravitational acceleration is the acceleration on an object caused by gravity. Neglecting friction such as air resistance, all small bodies accelerate in a gravitational field at the same rate relative to the center of mass.

Friend you are very curious man. I can't give you the all answers. Everything is simply given on our NCERT books. But I want to suggest you that "Pradeep Books" are best for XI physics.

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help us palz...we need ur help..

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derive the necessary relation for variation of g with depth?Answer dis pleasee>>>

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Newton's law of gravitaion states that every body in the universe attracts evry other body by an attractive force which is directly proportional to the product of the massess of the bodies and is inversely proportional to the square of the distance between them.

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i think u should read out ur book

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hey plz search their ans on google .or use pra deep.these are the best options to get ans....

thank u..

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8. (a) Law of orbits- All planets revolve around the sun in an elliptical orbit with sun at one of its focii.

(b) Law of area- It states that the line joining the centre of sun and centre of planet sweeps out equal area at equal intervals of time i.e. aerial velocity of planet remains constant.

(c) Law of timeperiods- It states that the square of timeperiod of a planet around the sun is directly proportional to the cube of average distance between the sun and planet.

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1. (i) Newton 's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

(ii) The gravitational constant denoted by letter G, is an empirical physical constant involved in the calculation(s) of gravitational force between two bodies.

2. gravitational acceleration is the acceleration on an object caused by gravity. Neglecting friction such as air resistance, all small bodies accelerate in a gravitational field at the same rate relative to the center of mass.

F=Gm'.m"/r^2

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refer pradeeps , dinesh ,etcits clearly written and described in them

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