Assertion & Reasoning Practice Worksheet
Gravitation โ Class 11 Physics (CBSE 2024โ25)
Prepared by Gear Institute, Panchkula
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.
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 Basic to Moderate
- The gravitational force between two bodies increases if the distance between them is reduced to half.
Reason: Gravitational force is inversely proportional to the square of the distance. (A) - The acceleration due to gravity is greater at poles than at the equator.
Reason: The Earth’s radius is smaller at poles. (A) - The value of G depends on the medium between the two masses.
Reason: Gravitational force acts through vacuum independent of the medium. (D) - A satellite moving in a circular orbit does not fall to Earth.
Reason: The gravitational force provides the necessary centripetal force. (A) - The weight of a body is zero in a freely falling elevator.
Reason: There is no normal reaction in free fall. (A) - The gravitational potential energy of a body is always positive.
Reason: It is zero at infinity and negative when bound to Earth. (D)
SET 2 โ Intermediate Level
- The potential at a point due to a spherical shell is the same anywhere inside it.
Reason: The field inside a shell is zero. (A) - At the center of Earth, gravitational field is zero.
Reason: All parts of Earth pull equally in opposite directions. (A) - The potential energy of a satellite decreases when moved to a lower orbit.
Reason: Magnitude of potential energy increases nearer to Earth. (A) - When a satellite goes to higher orbit, total energy increases.
Reason: Increase in potential energy > decrease in kinetic energy. (A) - Escape velocity does not depend on the mass of the object.
Reason: It depends on Earth’s mass and radius only. (A) - The value of g increases if Earth’s radius shrinks.
Reason: g is inversely proportional to Rยฒ. (A) - Orbital speed is independent of satellite’s mass.
Reason: m cancels out in gravitational and centripetal equations. (A) - Escape velocity ensures the body never returns.
Reason: Total energy becomes zero at escape speed. (A) - If Earth shrinks to one-fourth radius, escape velocity doubles.
Reason: vโ โ 1 / โR. (A) - Work done by gravity depends on path taken.
Reason: Gravitational force is conservative. (D) - Potential energy of two masses is positive at finite distance.
Reason: U = 0 at infinity and negative at finite separation. (D) - g at depth d is g (1 โ d / R).
Reason: Only inner mass (R โ d) contributes to g. (A) - Keplerโs second law shows areal velocity constant.
Reason: Gravitational force is always towards the Sun. (A) - Gravitational potential is scalar but field is vector.
Reason: Potential = energy / mass, Field = force / mass. (A) - Planet moves fastest at aphelion.
Reason: Potential energy minimum at aphelion. (D) - Potential energy = 0 at infinity.
Reason: Work done to infinity = |U|. (A) - Total energy of a planet is negative.
Reason: Kinetic energy = ยฝ |Potential energy| but positive. (A) - An object in a tunnel through Earth executes SHM.
Reason: Force is directly proportional to distance from the center. (A) - Gravitational potential decreases toward the center.
Reason: It is most negative at the center. (A) - The field at the center of a semicircular ring is zero.
Reason: Horizontal components cancel, leaving vertical. (C)
Answer Key
SET 1: 1-A, 2-A, 3-D, 4-A, 5-A, 6-D
SET 2: 1-A, 2-A, 3-A, 4-A, 5-A, 6-A, 7-A, 8-A, 9-A, 10-D,
11-D, 12-A, 13-A, 14-A, 15-D, 16-A, 17-A, 18-A, 19-A, 20-C
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