NEET Physics: Rotational Motion Practice Questions
14 free multiple-choice questions on Rotational Motion for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more Rotational Motion questions in the app →Q1. Which condition must be met for the angular momentum of a system to be conserved?
Show answer & explanation
Correct answer: A — The net external torque acting on the system is zero
Angular momentum is conserved if and only if the net external torque acting on the system is zero (τₙₑₜ = 0).
Q2. Which physical quantity measures the amount of rotation of a body divided by the radius of the circle traced by the body?
Show answer & explanation
Correct answer: D — Angular displacement
Angular displacement (θ) is defined as the ratio of the arc length (the amount of rotation) to the radius of the circle (s/r), which is the fundamental concept of rotational movement.
Q3. The moment of inertia of a body is a measure of its resistance to:
Show answer & explanation
Correct answer: D — Rotational motion
The moment of inertia is the rotational analogue of mass; it measures an object's resistance to changes in its rotational motion.
Q4. The centre of mass of a system is defined as the point where the weighted average of the positions of all the particles is taken. Which statement is true regarding the centre of mass?
Show answer & explanation
Correct answer: D — It is the point where the system experiences zero resultant force.
The centre of mass is the average position of the mass distribution. While forces and torques relate to motion, the CM is fundamentally a property describing the distribution of mass. It is not necessarily where the resultant force acts or where zero torque exists (unless the system is in equilibrium).
Q5. If the mass distribution of a body is concentrated further away from the axis of rotation, the moment of inertia of the body will generally:
Show answer & explanation
Correct answer: C — Increase
Moment of inertia is proportional to the square of the distance from the axis of rotation. Increasing the distance increases the moment of inertia.
Q6. If the angular velocity of a body is constant, what can be inferred about its angular acceleration?
Show answer & explanation
Correct answer: C — Angular acceleration is zero
If angular velocity is constant, the rate of change of angular velocity (angular acceleration) must be zero.
Q7. In a system of two particles, if the center of mass is stationary, it implies that:
Show answer & explanation
Correct answer: A — The net external force acting on the system is zero
If the center of mass is stationary, by the definition of the center of mass, the net external force acting on the entire system must be zero (F⃗ₙₑₜ = Ma⃗₍CM) = 0).
Q8. The concept of the center of mass is essential in analyzing rotational motion because it relates the linear motion of the body to its rotational properties. Which property is directly related to the distribution of mass about the center of mass?
Show answer & explanation
Correct answer: C — Moment of inertia.
The moment of inertia is the rotational analogue of mass, describing the resistance to changes in rotational motion, and it is calculated relative to the center of mass.
Q9. If the moments of inertia about the three mutually perpendicular axes (x, y, z) are Iₓ, I_y, and I_z respectively, which statement correctly describes the relationship using the perpendicular axis theorem for relating these quantities?
Show answer & explanation
Correct answer: B — Iₓ² + I_y² = I_z²
The perpendicular axis theorem, when applied to the relationship between the principal moments of inertia (or components related to them), results in the Pythagorean relationship: Iₓ² + I_y² = I_z². This is the defining relationship derived from the concept of perpendicular axes.
Q10. What is the centre of mass (CM) of a particle, according to the definition in rotational mechanics?
Show answer & explanation
Correct answer: D — The average position of all mass elements of the body.
The centre of mass is the average position of all the mass elements of a body.
Q11. If the angular velocity of a rotating body is constant, what can be said about its angular acceleration?
Show answer & explanation
Correct answer: A — It must be zero
Angular acceleration (α) is the rate of change of angular velocity (ω). If ω is constant, then α= 0.
Q12. A body moving in a circle has a constant angular acceleration. This implies that its linear acceleration has a component directed towards the center, known as:
Show answer & explanation
Correct answer: D — Centripetal acceleration
When an object moves in a circle with constant angular acceleration, it experiences a centripetal acceleration directed towards the center of the circle, which is responsible for the change in direction.
Q13. Consider two particles A and B moving such that their centre of mass is stationary. This implies that the net external force acting on the system is:
Show answer & explanation
Correct answer: A — Zero
If the centre of mass of a system is stationary, the system is in equilibrium (or moving with constant velocity), meaning the net external force acting on the system must be zero (Newton's First Law extension).
Q14. A larger distance (r) between the point of application of the force and the pivot point results in a larger torque, assuming the force remains constant. This is because:
Show answer & explanation
Correct answer: C — Torque is directly proportional to the product of r and F.
Since τ= rF, torque is directly proportional to the distance r when the force F is constant.
Keep going — practice on Padhai Karlo
Padhai Karlo gives you unlimited NEET practice: chapter-wise questions, timed quizzes, and full mock tests with an All-India Rank — free to start.
Get the free Android app →