Rotational Motion – Stage 2 (Page 7)

Objective Type Questions – Level II (With Explanations)

These MCQs test conceptual clarity + application. They are commonly seen in Board objective sections and JEE Main.

Q11.

If the radius of a rotating disc is doubled and mass remains same, its moment of inertia about the same axis becomes:

A) I/2
B) 2I
C) 4I
D) I

Correct Answer: C
Explanation: I ∝ MR². If R doubles → I becomes 4 times.

Q12.

A particle moves in a circular path with constant speed. Which of the following is conserved?

A) Velocity
B) Angular momentum about the center
C) Linear momentum
D) Force

Correct Answer: B
Explanation: Torque about the center is zero, hence angular momentum is conserved.

Q13.

A uniform rod is rotated about one end. Its moment of inertia is:

A) ML²/12
B) ML²/3
C) ML²/2
D) ML²

Correct Answer: B
Explanation: Using parallel axis theorem: I = ML²/3.

Q14.

In rolling motion without slipping, friction:

A) Always opposes motion
B) Always does positive work
C) Always does negative work
D) May do zero work

Correct Answer: D
Explanation: In pure rolling, static friction does no work.

Q15.

A disc and a ring roll down an incline without slipping. Which statement is correct?

A) Both reach together
B) Ring reaches first
C) Disc reaches first
D) Depends on mass

Correct Answer: C
Explanation: Disc has smaller moment of inertia → greater acceleration.

Q16.

If no external torque acts on a rotating body, which quantity remains constant?

A) Angular velocity
B) Angular acceleration
C) Angular momentum
D) Moment of inertia

Correct Answer: C
Explanation: Law of conservation of angular momentum.

Q17.

The quantity that decides resistance to change in angular motion is:

A) Torque
B) Angular velocity
C) Angular momentum
D) Moment of inertia

Correct Answer: D
Explanation: Moment of inertia resists angular acceleration.

Q18.

A wheel rotating with angular velocity ω is brought to rest. Which quantity becomes zero first?

A) Angular velocity
B) Angular acceleration
C) Torque
D) Moment of inertia

Correct Answer: B
Explanation: When motion stops, angular acceleration becomes zero first.

Objective Exam Strategy

✔ Recall standard M.I. formulas
✔ Identify axis clearly
✔ Use elimination method
✔ Visualize rolling and torque direction

Next: Phase 1 – IIT/JEE Solved Problems (Basic → Moderate)

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