CBSE Class 11 Physics โ Gravitation (Assertion & Reason) โ Set 2
Prepared by Gear Institute, Panchkula โข Based on CBSE 2024โ25 Pattern โข Mobile Friendly
Instructions
Choose the correct option:
- (A) Both Assertion and Reason are true, and Reason is the correct explanation.
- (B) Both Assertion and Reason are true, but Reason is not the correct explanation.
- (C) Assertion is true but Reason is false.
- (D) Assertion is false but Reason is true.
Set 1 โ Conceptual to Moderate
1. The gravitational field inside a uniform solid sphere increases linearly with distance from the center.
Reason: Only the mass enclosed within that radius contributes to the gravitational force.
Answer: (A)
2. The value of gravitational potential at infinity is taken as zero.
Reason: The work done in bringing a unit mass from infinity to that point equals the potential.
Answer: (A)
3. The acceleration due to gravity is the same for all bodies irrespective of their masses.
Reason: Gravitational force is proportional to the mass of the body.
Answer: (A)
4. The orbital speed of a satellite decreases as its orbit height increases.
Reason: At greater heights, gravitational pull of Earth is weaker.
Answer: (A)
5. Two satellites revolving around Earth at the same height but different masses have equal kinetic energies.
Reason: Kinetic energy of a satellite in orbit depends on its own mass.
Answer: (C)
6. The gravitational potential at the Earthโs surface is -GM/R.
Reason: Work is done by the gravitational force when a body falls toward Earth.
Answer: (B)
Set 2 โ Intermediate to Tough
7. For a body projected at less than escape velocity, its path is a closed orbit.
Reason: When total energy is negative, motion under gravity is bound.
Answer: (A)
8. The gravitational potential due to a spherical shell of mass M at a distance r (> R) is -GM/r.
Reason: The shell behaves as if all its mass were concentrated at its center for external points.
Answer: (A)
9. The gravitational force between two particles separated by distance r is F. If both masses are doubled, the force becomes 4F.
Reason: Gravitational force is directly proportional to the product of their masses.
Answer: (A)
10. The potential energy of an artificial satellite is -2 times its kinetic energy.
Reason: The total energy of the satellite is negative and equals potential plus kinetic energy.
Answer: (A)
11. The gravitational potential energy between Earth and Moon is positive.
Reason: The reference point of zero potential energy is taken at infinity.
Answer: (D)
12. At the same height, the gravitational potential is the same everywhere on Earth.
Reason: The Earth is a perfect sphere.
Answer: (D)
13. A communication satellite must revolve around Earth in the equatorial plane.
Reason: Only in that plane can it maintain a fixed position relative to Earthโs surface.
Answer: (A)
14. The time period of a geostationary satellite depends only on the mass of the satellite.
Reason: The time period is determined by Earthโs gravitational field and orbital radius, not the satelliteโs mass.
Answer: (C)
15. The work done by gravity in moving a mass from one point to another in a gravitational field is zero.
Reason: The gravitational force is conservative.
Answer: (B)
16. The potential due to two equal masses at equal distances on either side of a point is zero, but the field is not zero.
Reason: The forces add as vectors while potentials add algebraically (scalars).
Answer: (A)
17. For a planet revolving around the Sun, the total mechanical energy per unit mass is -GM/2r.
Reason: The planetโs potential energy is -GM/r and kinetic energy is +GM/2r.
Answer: (A)
18. The energy required to remove a satellite from its orbit to infinity equals the magnitude of its total energy.
Reason: The total energy of a satellite in circular orbit is -GMm/2r.
Answer: (A)
19. Inside a spherical shell, the gravitational potential is constant.
Reason: The gravitational field inside a shell is zero.
Answer: (A)
20. A man standing on the Moonโs surface experiences weight one-sixth that on Earth.
Reason: The Moonโs mass and radius are smaller than Earthโs.
Answer: (A)
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