Rotational Motion Important Questions for NEET Physics - 2026

1. Multiple choice questions.

Q1. The moment of inertia of a thin uniform rod of mass $M$ and length $L$ about an axis passing through its centre and perpendicular to its length is:

• (a) $\dfrac{1}{12}ML^2$
• (b) $\dfrac{1}{3}ML^2$
• (c) $\dfrac{1}{2}ML^2$
• (d) $ML^2$

Answer: (a) $\dfrac{1}{12}ML^2$.

Q2. Which physical quantity does not change during the rotation of a rigid body if no external torque is applied?

• (a) Torque
• (b) Angular momentum
• (c) Angular velocity
• (d) Moment of inertia

Answer: (b) Angular momentum.

Q3. The radius of gyration of a body is defined as:

• (a) The distance from axis to centre of mass
• (b) Root mean square distance of body’s particles from the axis
• (c) Geometric mean distance from axis
• (d) None of these

Answer: (b) Root mean square distance of body’s particles from the axis.

Q4. The parallel axis theorem applies only to:

• (a) Non-rigid bodies
• (b) Rigid bodies
• (c) Point particles
• (d) Fluids

Answer: (b) Rigid bodies.

2. Very Short Answer (VSA).

Q1. What is meant by centre of mass?

Answer: Centre of mass is the point where the total mass of a body or system is considered to be concentrated for motion analysis.

Q2. Define angular velocity.

Answer: Angular velocity is the rate of change of angular displacement of a body with respect to time, measured in radians per second.

Q3. Write the SI unit of torque.

Answer: The SI unit of torque is newton-metre (N·m).

3. Short Answer Questions.

Q1. State and explain the law of conservation of angular momentum with an example.

Answer: The law states that if no external torque acts on a system, its total angular momentum remains constant. For example, a figure skater spins faster when she pulls her arms in, because the moment of inertia decreases, so angular velocity increases, keeping angular momentum constant.

Q2. Differentiate between centre of mass and centre of gravity for a rigid body.

Answer: The centre of mass is the point representing the mean position of all masses. The centre of gravity is the point where the entire weight acts. In a uniform gravitational field, both points coincide, but they can differ if gravity is non-uniform.

Q3. Write the statement and proof of the perpendicular axis theorem.

Answer: The perpendicular axis theorem states that for a planar body, $I_z = I_x + I_y$, where $z$ is perpendicular to the plane and $x, y$ lie in the plane. The proof uses the relation $r^2 = x^2 + y^2$ for mass elements.

4. True or False Questions.

Q1. The moment of inertia of a body depends on the distribution of mass about the axis of rotation.

Answer: True.

Q2. Torque produces linear acceleration in a body.

Answer: False.

Q3. For a given angular momentum, a larger moment of inertia means a smaller angular velocity.

Answer: True.

3. Fill in the Blanks Questions.

Q1. The rotational analogue of force is called ________.

Answer: torque

Q2. The SI unit of angular momentum is ________.

Answer: kilogram metre$^2$ per second (kg·m$^2$/s)

Q3. According to the parallel axis theorem, $I = I_\text{cm} + M d^2$, where $d$ is the ________ between the two axes.

Answer: perpendicular distance

Why Rotational Motion Matters for NEET Physics Aspirants

Understanding rotational motion boosts your NEET Physics score by making concepts like torque and moment of inertia easy. Practicing important questions helps you spot patterns and solve tricky problems faster. With Vedantu's curated list, revision becomes simple and stress-free.

Solve diverse questions on angular momentum, the centre of mass and conservation laws to build confidence. Consistent practice of these NEET-level problems ensures you gain clarity in every subtopic and remain exam-ready every step of the way.

Let expert guidance shape your preparation journey with Vedantu's Physics important questions. Stay focused on gaining deep understanding of rigid body rotation, reflecting the real NEET Physics challenges. Quick revision and regular tests will set you up for success in NEET 2026.