NCERT  //  Physics  //  Ch.6

System of Particles and Rotational Motion
MCQ_MASTER_SERIES

Centre of Mass · Torque & Moment of Inertia · Angular Momentum

[ 50 QST ]
[ 45 min ]
[ 3 TIERS ]
[ 6 TOPICS ]
⚡ INIT_QUIZ // ANALYTICS
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Question Intelligence

Quiz Analytics

A data-driven breakdown of all 50 questions by difficulty, exam origin and topic distribution.

📈 Distribution Overview

50
Total Questions
Concept Check (NCERT)
24
Boards / JEE Main
18
JEE/NEET Edge Cases
8

🗂 Topic Coverage

System of Particles & COM
20%
Linear Momentum & Impulse
16%
Torque & Angular Momentum
20%
Moment of Inertia & Theorems
20%
Pure Rotation & Rolling Motion
16%
Conservation Laws & Examples
8%
24
Concept Check (NCERT)
18
Boards / JEE Main
8
JEE/NEET Edge Cases
Conceptual Framework

Key Concept Highlights

6 foundational pillars that power every question in this quiz. Understand these, and the answers follow naturally.

🎯
System of Particles & Centre of Mass
A system of particles behaves as if its entire mass were concentrated at a single point called the centre of mass, whose motion is governed only by external forces.
⚖️
Linear Momentum & COM Motion
The total linear momentum of a system equals the product of total mass and velocity of the centre of mass; with no external force, COM moves with uniform velocity.
🌀
Torque & Rotational Dynamics
Torque measures the turning effect of a force about an axis and is given by the cross product of position vector and force, producing angular acceleration.
📀
Moment of Inertia
Moment of inertia quantifies rotational inertia and depends on how mass is distributed about the axis; larger values mean greater resistance to change in rotational motion.
↻
Angular Momentum & Its Conservation
Angular momentum is the rotational analogue of linear momentum and remains conserved when the net external torque on the system is zero.
🚴
Pure Rotation & Rolling Motion
In pure rotation all particles move in circles about a fixed axis, while rolling without slipping combines translation of the centre of mass with rotation about an instantaneous axis at the contact point.
Pedagogical Value

Why MCQs Matter

Multiple-choice questions are not mere guessing games — they are the sharpest diagnostic tool available to a competitive exam aspirant.

~12–15%

of Class XI Mechanics weightage across Boards & JEE/NEET (via COM, torque, rolling motion & rotational dynamics)

Quick Reference

Important Formula Capsules

10 must-memorise equations that surface repeatedly across CBSE and JEE papers.

Centre of Mass (discrete)
\[ \vec{R}_{\text{CM}} = \dfrac{\sum_i m_i \vec{r}_i}{\sum_i m_i} \]
Linear Momentum (system)
\[ \vec{P} = M \vec{V}_{\text{CM}} \]
Torque (vector)
\[ \vec{\tau} = \vec{r} \times \vec{F} \]
Rotational Dynamics
\[ \tau = I\alpha \]
Moment of Inertia
\[ I = \sum_i m_i r_i^2 \]
Angular Momentum (particle)
\[ \vec{L} = \vec{r} \times \vec{p} \]
Angular Momentum (rigid)
\[ L = I\omega \]
Rotational KE
\[ K = \dfrac{1}{2} I \omega^2 \]
v–ω Relation (rolling)
\[ v = \omega R \]
Angular Acceleration
\[ \alpha = \dfrac{d\omega}{dt} \]
Learning Outcomes

What You Will Learn

By completing this quiz set you will have exercised all the following competencies.

01 Define and locate the centre of mass for simple systems like two-particle systems, rods and rings.
02 Relate motion of the centre of mass to total external force and total linear momentum of a system.
03 Explain and calculate torque, moment of inertia and angular momentum for standard rigid bodies about given axes.
04 Use τ = Iα and L = Iω to solve numerical problems on rotational dynamics and conservation of angular momentum.
05 Distinguish between pure translation, pure rotation and rolling motion, including the condition of rolling without slipping.
06 Apply theorems of parallel and perpendicular axes to compute moment of inertia of composite bodies.
07 Analyse everyday situations such as opening doors, spinning skaters and rolling wheels using rotational dynamics and COM concepts.
Exam Preparation

Strategy & Preparation Tips

5 evidence-based strategies to maximise your score in CBSE Boards and JEE.

Step 01
Nail COM & Momentum Basics
Start with centre of mass definitions and simple two-particle examples, then connect total linear momentum with motion of COM for easy conceptual and 1-mark questions.
Step 02
Torque & Axis Sense
Practise right-hand rule, sign convention and r×F geometry so that direction of torque and angular momentum in MCQs never confuses you.
Step 03
Moment of Inertia Library
Memorise standard I formulae (rod, ring, disc, sphere) and parallel/perpendicular axis theorems; most board and JEE Main numericals are direct applications.
Step 04
Conservation of L Problems
Solve classic examples like spinning skater, collapsing neutron star and rotating stools to master how I and ω adjust when external torque is zero.
Step 05
Rolling & v = ωR Intuition
Focus on rolling without slipping, instantaneous rest at the contact point, and v = ωR relation to crack typical mixed translation–rotation questions.

Ready to Test Your Mastery?

50 questions  ·  Elapsed timer  ·  Instant scored results

⚡ Begin System of Particles and Rotational Motion Quiz
🎯 Knowledge Check

Physics — SYSTEMS OF PARTICLES AND ROTATIONAL MOTION

50 Questions Class 11 MCQs
1
A system of particles is best described as
2
The centre of mass of a system depends on
3
If no external force acts on a system, the centre of mass
4
Translational motion of a rigid body means
5
In pure rotational motion, each particle moves in
6
The axis of rotation is
7
Angular displacement is measured in
8
Angular velocity is defined as
9
Which quantity is same for all particles in rotational motion?
10
Torque is the rotational analogue of
11
The SI unit of torque is
12
Moment of inertia depends on
13
The SI unit of moment of inertia is
14
Greater the moment of inertia of a body
15
Angular momentum is conserved when
16
Rolling motion is a combination of
17
In rolling without slipping, the point of contact is
18
Linear momentum of a system equals
19
A rigid body differs from a particle because
20
For a rigid body in pure translation, angular velocity is
21
The centre of mass of a uniform rod lies
22
If a body rotates about its centre of mass, the COM
23
Torque is maximum when force acts
24
Which is conserved in absence of external force?
25
Which is conserved in absence of external torque?
26
The relation between linear and angular velocity is
27
Angular acceleration is caused by
28
A door opens easily when pushed
29
Which quantity changes when arms of a skater are folded?
30
In the above case, angular velocity
31
Moment of inertia plays the role of
32
The kinetic energy of a rotating body depends on
33
For the same torque, angular acceleration is
34
The centre of mass of a projectile follows
35
Internal forces in a system
36
Which quantity is vector in rotational motion?
37
A couple produces
38
Angular momentum depends on
39
If the radius doubles, linear velocity becomes
40
Which motion best represents combined motion?
41
The instantaneous axis of rotation
42
For a rigid body, distances between particles
43
In absence of gravity, centre of mass of a system
44
Rotational kinetic energy is given by
45
If torque is zero, angular acceleration is
46
The COM of an exploding object
47
Which factor does NOT affect moment of inertia?
48
Angular momentum is defined as
49
When a body rotates faster without external torque, its
50
Conservation of angular momentum is most useful in
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Frequently Asked Questions

A system of particles is a collection of two or more particles considered together to study their combined motion.

Studying systems simplifies analysis by focusing on collective properties like centre of mass and total momentum.

A rigid body is an ideal body in which the distance between any two particles remains constant under applied forces.

It is motion in which all particles of the body move with the same velocity and acceleration at any instant.

Rotational motion is the motion of a body about a fixed axis where all particles move in circular paths.

It is an imaginary straight line about which a rigid body rotates.

The centre of mass is the point representing the average position of the mass of a system.

Yes, in some cases like a ring or a bent object, the centre of mass lies outside the material body.

Only external forces acting on the system govern the motion of the centre of mass.

The centre of mass remains at rest or moves with constant velocity.

It is the vector sum of the momenta of all particles in the system.

If the net external force on a system is zero, its total linear momentum remains constant.

It is the angle through which a body rotates about a fixed axis.

Angular velocity is the rate of change of angular displacement with time.

It is the rate of change of angular velocity with time.

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