Questions on chapter Gravitation(Class-XI LEVEL)

GRAVITATION
1.       State and explain Newton’s law of gravitation. Hence define Gravitational Constant G. What is its value in SI?
2.       Define acceleration due to gravity. Discuss the variation of acceleration due to gravity with-i) the altitude ii) the depth and iii) the shape of the earth.
3.       Discuss the variation of acceleration due to gravity due to rotation of earth. What is the effect on g at poles and equator of the earth due to rotation of earth?
4.       Derive the relation
                                     g = GM/R2  for acceleration due to gravity of the earth,where M and R are the mass and radius of the earth.
5.       Show that the acceleration of free fall g at the surface of earth and the gravitational constant G are related by the expression
                         g = 4/3 πρGR, where ρ is mean density of the earth and R, radius of the earth.
6.       State and explain Kepler’s laws of planetary motion.
7.       State Kepler’s laws of planetary motion and deduce Newton’s law of gravitation from Kepler’s law.
8.       Discuss the effect of depth on acceleration due to gravity. What is its value at the centre of the earth?
9.       Prove that the distance we have to cover into earth below its surface is two times the distance we have to cover above the surface to get the same change in the value  of g .
1.   Show that Kepler’s second law follows from the law of conservation of angular momentum.
1.   According to Newton ‘s law of gravitation the  apple and the earth experience equal and opposite forces due to gravitation .but it is the apple that falls towards the earth and not vice –versa. Why?
1.   If the diameter of earth becomes two times its present and its mass remains unchanged; then how would the weight of an object on the surface of the earth be affected?
1.   Does acceleration due to gravity depend upon the mass of a planet? Explain.
1.   Do the forces of friction and other contact forces arise due to gravitation attraction? if not,what is the origin of these forces?
1.     Four equal masses are placed at the four corners of a square. What is the intensity of gravitati onal field at the point intersection of the diagonals of the square?
1.   Why do the stars appear displaced away from the sun?
1.   Dose the change in gravitational potential energy of a body between two points depend upon the nature of path followed? Explain
1.   Define gravitational field and intensity of gravitational field. Give its SI unit.
1.   Show that the gravitational field and potential at any point on the surface of the earth are g and g R respectively .The earth may be assumed to be a sphere of uniform density.
2.   Explain the terms gravitational field and the gravitational potential energy.
2.   Define gravitational potential and hence derive expression for it.
2  Define escape velocity. Derive an expression for escape velocity of an object from the surface of a planet.
2.   Briefly explain why there is practically no atmosphere on the sueface of the moon.
2.   Why dose hydrogen escape faster from earth’s atmosphere than oxygen.
2.   The artificial satellite does not have any fuel, but even then it remains orbiting around the earth. Why? Explain.
2.   If a satellite going around the earth suddenly loses weight, will there be a change in time period of the satellite?
2.   Air friction increases the velocity of the satellite. Explain.
2.   A satellite with kinetic energy EK  is revolving round the earth in a circular orbit. How much more kinetic energy should be given, so that it may just escape into the outer space?
2.   If T is the period of a satellite revolving just above the surface of a plate, whose average density is ρ, show that ρ T2 is a universal constant.
3.   What is the difference between ordinary and geostationary satellite?
3.   A body has a sense of weightlessness in a satellite revolving around the earth. Why? Moon is a satellite of earth, but there is no weightlessness condition on it. Explain.
3.   What do mean by geostationary satellite and parking orbit? Show that height of a geostationary satellite from the surface of earth is 36000km.
3.   What are lighter gaseous elements, like hydrogen, helium etc., rare in the earths atmosphere? Two artificial satellites of different masses are revolving round the earth at the same altitude. When one will be moving faster? Justify your answer?
3.   Derive the expressions for-i) kinetic energy ii) potential energy and iii) total energy of an artificial satellite. Also draw their graphical variation with position.
3.   Show that everything become weightless on earth’s surface (or, fly from earth)  if rotational speed of earth is increased 17th times of the present value.
3.   Show that the escape velocity of earth is 11.2km/s. Show that moon will escape from earth’s atmosphere if its speed is increased by 41.42 %.
3.   What do mean by weight of a body? Show that weight of a body becomes zero at the centre of earth.
3.   What will the weight of a body on the surface of earth, if earth is considered a hollow sphere?
3.   What do you mean by orbital velocity of an artificial satellite? Derive and expression for it. Show that time period and orbital velocity of a satellite don’t depends upon mass of the satellite.
40.   Derive a relation between orbital velocity and escape velocity of a satellite rotating very close to earth.

41.   What do you mean by a polar satellite? Write a short note on uses of a satellite.

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