# Conceptual Questions Based on Class 11 Physics Gravitation

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Here we are providing conceptual questions for Class 11 Physics Gravitation. Answers are also provided along with questions. So that students can read and understand the question. These questions are prepared by the subject experts. Students can read these conceptual questions based on Gravitation for better topic clarity and therefore will be able to score better marks in their exam.

## Conceptual Questions Based on Class 11 Physics Gravitation

Conceptual questions based on Class 11 Physics Chapter 7 Gravitation is given below. Go through each and every question to understand the topic clearly.

Q.1. The mass of the moon is nearly 10% of the mass of the earth. What will be the gravitational force of the earth on the moon, in comparison to the gravitational force of the moon on the earth?

Solution. Both forces will be equal in magnitude as gravitational force between two bodies is a mutual force.

Q.2. Does the concentration of the earth’s mass near its centre change the variation of g with height compared with a homogeneous sphere? How?

Solution. Any change in the distribution of the earth’s mass will not affect the variation of acceleration due to gravity with height. This is because for a point outside the earth, the whole mass of the earth is ‘effective’ and the earth behaves as a homogeneous sphere.

Q.3. Earth is continuously pulling the moon towards its centre, still it does not fall to the earth. Why?

Solution. Gravitational force of attraction due to earth provides the centripetal force, which keeps the moon in orbit around the earth. Moreover, this gravitational force acts perpendicular to the velocity of the moon.

Q.4. Why do you feel giddy while moving on a merry-go-round?

Solution. When moving in a merry-go-round, our weight appears to decrease when we move down and appears to increase when we move up.

Q.5. We cannot move finger without disturbing all stars. Why?

Solution. When we move our finger, the distance between the objects and our finger changes. Hence, the force of attraction changes, disturbing the entire universe, including the stars.

Q.6. When dropped from the same height a body reaches the ground quicker at poles than at the equator. Why?

Solution. The acceleration due to gravity is more at the poles than at the equator. When the initial velocities and distances travelled are the same, the time taken by the body is smaller if the acceleration due to gravity is large. Hence, when dropped from the same height, a body reaches the ground quicker at the poles than at the equator.

Q.7. Which is more fundamental-mass or weight of a body?

Solution. Mass is more fundamental than weight because the mass of a body remains constant while its weight changes from place to place due to change in the value of g.

Q.8. Does a rocket really need the escape velocity of 11.2 kms-1 initially to escape from the earth?

Solution No, rocket can have any velocity at the start. The rocket can continue to increase the velocity due to thrust provided by the escaping gases that will carry it to a desired position.

Q.9. The moon has no atmosphere. Why?

Solution Due to the small value of ‘g’, the escape velocity on the moon surface is small (2.38 kms-1). The air molecules have thermal velocities greater than the escape velocity. Therefore, the air molecules escape away and cannot form atmosphere on the moon.

Q.10. Moon-travellers tie heavy weight at their back before landing on the moon. Why?

Solution. Due to the small value of g on the moon, the traveller would weigh less. To compensate for this loss in weight, the travellers load their backs with heavy weight.

Q.11. Why is a multi-stage rocket required to launch a satellite?

Solution. The multistage rocket helps to economise the consumption of fuel.

Q.12. A satellite of small mass bums during its descent and not during ascent. Why?

Solution. The speed of the satellite during descent is much larger than that during its ascent. As the air resistance is directly proportional to velocity, so heat produced during descent is very large and the satellite bums up.

Q.13. Why an astronaut in an orbiting spacecraft is not in zero gravity although weightless?

Solution. The astronaut in the orbiting spacecraft is still in the gravitational field of the earth and experiences appreciable gravity. However, the gravity is used up in providing the necessary centripetal force.

Q.14. Why are space rockets usually launched from west to east in the equatorial plane?

Solution. Due to rotation of the earth about its polar axis, every particle on the earth has a linear velocity directed from west to east. This velocity (v = RÏ‰) is maximum at the equator. When a rocket is launched from west to east, this maximum velocity gets added to the launching velocity, so the launching becomes easier.

Q.15. The artificial satellite does not have any fuel, but even then it remains in its orbit around the earth. Why.

Solution. The centripetal force necessary for orbital motion of the satellite is provided by the force of gravitation exerted by the earth on the satellite. So, the satellite does not need any fuel for its orbital motion.

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