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.

Due to paucity of time it would not be possible for us to provide the answers to all your queries. We are providing solutions to some your good queries. Try solving rest of the questions yourself and if you face any difficulty then do get back to us.

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 = $\frac{G{m}_{1}{m}_{2}}{{r}^{2}}\phantom{\rule{0ex}{0ex}}whereGisagravitationalcons\mathrm{tan}t=6.67X{10}^{-11}N{m}^{2}k{g}^{-2}\phantom{\rule{0ex}{0ex}}ThedimensionalformulaforGis\left[{M}^{-1}{L}^{3}{T}^{-2}\right]$

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$(1-\frac{d}{R})\phantom{\rule{0ex}{0ex}}$

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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