NEET PhysicsUpdated 19 Oct 2026

System of Particles and Rotational Motion: NEET PYQs and weightage

System of Particles and Rotational Motion carries 5.3 of 100 Physics marks in NEET by past-paper share: 40 of the 758 tagged NEET Physics PYQs in the ViJEEta bank (NEET 2013–2026). It ranks 4 of 30 Physics chapters.

Take the 25-question System of Particles and Rotational Motion test Formula sheet ↓All NEET Physics chapters

5.3/100 Weight in Physics

Exam importance (4/5, by past-paper share)

40 NEET PYQs

515 Practice questions

445 With measured difficulty

How the weight is computed: this chapter's tagged NEET PYQs divided by all tagged NEET Physics PYQs in the bank (40 of 758), times 100, with repeated questions counted once. The bank does not store the year of each NEET question, so none is printed. Computed from the bank at build time. Updated 19 Oct 2026.

System of Particles and Rotational Motion: formula sheet for NEET

14 formulas, each with when to use it. Copy it onto one page of your notebook: that page is this chapter's handbook.

Torque
$τ = r \times F$
$∣ τ ∣ = r F sin θ = r_{⊥} F$
Use it when: A force tries to turn a body. Take $r$ from the pivot and $θ$ between $r$ and $F$ .
Newton's 2nd law for rotation
$τ = I α$
Use it when: You need the angular acceleration of a body turning about a fixed axis. Pulleys and wound-string flywheels are the usual cases.
Moment of inertia
$I = \sum m_{i} r_{i}^{2} = M k^{2}$
Use it when: You have point masses, or you need the radius of gyration $k$ . Each $r_{i}$ is the perpendicular distance from the axis. Unit is $kg m^{2}$ .
Standard I values
$Ring, about axis through centre ⊥ plane: M R^{2}$
$Ring, about a diameter: \frac{M R ^{2}}{2}$
$Disc, about axis ⊥ plane: \frac{M R ^{2}}{2}$
$Disc, about a diameter: \frac{M R ^{2}}{4}$
$Rod, about midpoint ⊥ rod: \frac{M L ^{2}}{12}$
$Hollow cylinder, about its axis: M R^{2}$
$Solid cylinder, about its axis: \frac{M R ^{2}}{2}$
$Solid sphere, about a diameter: \frac{2 M R ^{2}}{5}$
Use it when: The body is a standard shape. Check the axis before you pick the value.
Parallel axis theorem
$I = I_{cm} + M d^{2}$
Use it when: The axis is parallel to an axis through the centre of mass, at a distance $d$ from it.
Rotational KE
$K = \frac{1}{2} I ω^{2}$
Use it when: You use energy conservation or work-energy for a spinning body.
Angular momentum
$L = I ω (body about a fixed symmetry axis)$
$l = r \times p$
$∣ l ∣ = r p sin θ = r_{⊥} p (particle)$
Use it when: A particle moves past a point, or a body spins about its symmetry axis.
Torque and angular momentum
$\frac{d L}{d t} = τ_{ext}$
Use it when: You are linking an external torque to how fast $L$ changes. Internal torques cancel.
Conservation of angular momentum
$I_{1} ω_{1} = I_{2} ω_{2} (if τ_{ext} = 0)$
Use it when: $I$ changes with no outside torque. Examples are a skater pulling in their arms, or a person on a swivel chair stretching out.
Rotational kinematics
$ω = ω_{0} + α t$
$θ - θ_{0} = ω_{0} t + \frac{1}{2} α t^{2}$
$ω^{2} = ω_{0}^{2} + 2 α (θ - θ_{0}) (constant α only)$
Use it when: $α$ is constant. Put $ω$ in rad/s ( $rpm \times 2 π /60$ ). Revolutions $= θ /2 π$ .
Linear and angular link
$v = ω r$
$a_{tan} = r α$
$a_{rad} = ω^{2} r = \frac{v ^{2}}{r}$
Use it when: You need the speed or acceleration of a point at distance $r$ from the axis.
Work and power by a torque
$W = \int τ d θ$
$P = τ ω$
Use it when: A torque turns a body through an angle, or you need the rate of doing work.
Centre of mass
$X = \frac{\sum m _{i} x _{i}}{M} (the same form for Y and Z)$
$M V_{cm} = P_{total}$
$M A_{cm} = F_{ext}$
Use it when: You need the CM position of a set of masses. Also use it for an explosion or decay: internal forces do not change the CM's motion.
KE of a system
$K = K^{'} + \frac{1}{2} M V^{2}$
Use it when: The body translates and moves about its CM at the same time. $K^{'}$ is the KE about the CM and $V$ is the CM speed.

Trap

Using I = I_A + Md² from an axis A that does not pass through the centre of mass. The parallel axis theorem only works from I_cm. To go between two non-CM axes, go through I_cm first.

How does NEET ask System of Particles and Rotational Motion?

8 real previous-year questions from this chapter, as printed in the paper, each with its worked solution. Answer the first one here with no sign-in.

Q1PhysicsNEET UG PYQKinematics of Rotational Motion about a Fixed Axis

Try right here · No sign-in

A uniform circular disc of radius 50 cm at rest is free to turn about an axis which is perpendicular to its plane and passes through its centre. It is subjected to a torque which produces a constant angular acceleration of 2.0 rad s

^{- 2}

. Its net acceleration (at a point on the periphery of the disc ) in ms

^{- 2}

at the end of 2.0 s is approximately

Answer key (A) & worked solution

Correct answer: Option A

Particle at periphery will have both radial and tangential acceleration a

_{t}

= Rα = 0.5 × 2 = 1 m/s

^{2}

ω = ω

_{o}

+ αt ω = 0 + 2 × 2 = 4 rad/sec a

_{c}

= ω

^{2}

R = (4)

^{2}

× 0.5 = 16 × 0.5 = 8 m/s

^{2}

_{t o t a l}

a_{p}^{2} + a_{c}^{2} = 1^{2} + 8^{2} \approx 8 m / s^{2}

Q2PhysicsNEET UG PYQDynamics of Rotational Motion about a Fixed Axis

A small object of uniform density rolls up a curved surface with an initial velocity ‘v’. It reaches up to a maximum height of

\frac{3 v ^{2}}{4 g}

with respect to the initial position. The object is

ARing

BSolid Sphere

CHollow Sphere

DDisc

Answer key (D) & worked solution

Correct answer: Option D

From the conservation of mechanical energy, we get

\frac{1}{2} M v^{2} (1 + \frac{K ^{2}}{R ^{2}}) = M g h

Given that,

h = \frac{3 v ^{2}}{4 g}

\Rightarrow \frac{1}{2} M v^{2} (1 + \frac{K ^{2}}{R ^{2}}) = M g (\frac{3 v ^{2}}{4 g})

∴ \frac{K ^{2}}{R ^{2}} = \frac{1}{2}

\to K^{2} = R^{2} \frac{1}{2}

But,

K = \frac{I}{M}

∴ \frac{I}{M} = R^{2} \frac{1}{2}

∴ I = \frac{1}{2} M R^{2}

So, the given object is a disc.

Q3PhysicsNEET UG PYQDynamics of Rotational Motion about a Fixed Axis

A disk and a sphere of the same radius but different masses roll off on two inclined planes of the same altitude and length. Which one of the two object gets to the bottom of the plane first?

ADisk

BSphere

CBoth reach at the same time

DDepends on their masses

Answer key (B) & worked solution

Correct answer: Option B

a = \frac{g sin θ}{1 + \frac{K ^{2}}{R ^{2}}}

for disc;

\frac{K ^{2}}{R ^{2}} = \frac{1}{2} = 0.5

for sphere;

\frac{K ^{2}}{R ^{2}} = \frac{2}{5} = 0.4

a (sphere) > a (disc)

∴

sphere reaches first

Q4PhysicsNEET UG PYQDynamics of Rotational Motion about a Fixed Axis

The ratio of the accelerations for a solid sphere (mass ‘m’ and radius ‘R’) rolling down an incline of angle ′ θ ′ without slipping and slipping down the incline without rolling is:

A2 : 5

B7 : 5

C5 : 7

D2 : 3

Answer key (C) & worked solution

Correct answer: Option C

a_{r o l l in g} = \frac{g sin θ}{1 + \frac{2}{5}} = \frac{5}{7} g sin θ

a_{s l i pp in g} = g sin θ

\frac{a _{r o l l in g}}{a _{s l i pp in g}} = \frac{5}{7}

Q5PhysicsNEET UG PYQDynamics of Rotational Motion about a Fixed Axis

A disc of radius 2 m and mass 100 kg rolls on a horizontal floor. Its centre of mass has speed of 20 cm/s. How much work is needed to stop it?

A30 kJ

B2 J

C1 J

D3 J

Answer key (D) & worked solution

Correct answer: Option D

Work required = change in kinetic energy Final KE = 0 Initial

K E = \frac{1}{2} m v^{2} + \frac{1}{2} I ω^{2} = \frac{3}{4} m v^{2}

= \frac{3}{4} \times 100 \times (20 \times 10^{- 2})^{2} = 3 J ∣ Δ K E ∣ = 3 J

Q6PhysicsNEET UG PYQMoment of Inertia

Three objects, A : (a solid sphere), B : (a thin circular disk) and C : (a circular ring), each have the same mass M and radius R. They all spin with the same angular speed ω about their own symmetry axes. The amounts of work (W) required to bring them to rest, would satisfy the relation

_{B}

> W

_{A}

> W

_{C}

_{A}

> W

_{B}

> W

_{C}

_{C}

> W

_{B}

> W

_{A}

_{A}

> W

_{C}

> W

_{B}

Answer key (C) & worked solution

Correct answer: Option C

Work done required to bring them rest

Δ W = Δ K E

Δ W = \frac{1}{2} I ω^{2}

Δ W \propto I

for same ω

W_{A} : W_{B} : W_{C} = \frac{2}{5} M R^{2} : \frac{1}{2} M R^{2} : M R^{2}

= \frac{2}{5} : \frac{1}{2} : 1

= 4 : 5 : 10

\Rightarrow W_{C} > W_{B} > W_{A}

Q7PhysicsNEET UG PYQAngular Momentum in Case of Rotation about a Fixed Axis

Two discs of same moment of inertia rotating about their regular axis passing through centre and perpendicular to the plane of disc with angular velocities

ω_{1}

and

ω_{2} .

They are brought into contact face to face coinciding the axis of rotation. The expression for loss of energy during this process is

I (ω_{1} - ω_{2})^{2}

\frac{I}{8} (ω_{1} - ω_{2})^{2}

\frac{1}{2} I (ω_{1} + ω_{2})^{2}

\frac{1}{4} I (ω_{1} - ω_{2})^{2}

Answer key (D) & worked solution

Correct answer: Option D

Loss of K.E

= \frac{1}{2} \frac{I _{1} I _{2}}{I _{1} + I _{2}} (ω_{1} - ω_{2})^{2}

= \frac{1}{2} \frac{I ^{2}}{( 2 I )} (ω_{1} - ω_{2})^{2}

= \frac{1}{4} I (ω_{1} - ω_{2})^{2}

Q8PhysicsNEET UG PYQAngular Momentum in Case of Rotation about a Fixed Axis

A solid sphere is rotating freely about its symmetry axis in free space. The radius of the sphere is increased keeping its mass same. Which of the following physical quantities would remain constant for the sphere?

ARotational kinetic energy

BMoment of inertia

CAngular velocity

DAngular momentum

Answer key (D) & worked solution

Correct answer: Option D

τ_{e x} = 0

So,

\frac{d L}{d t} = 0

i.e. L = constant So angular momentum remains constant.

Which topics in System of Particles and Rotational Motion carry the most questions?

All 11 topics, by tagged PYQs, then practice questions. Counted from the bank. Updated 19 Oct 2026.

Topic	PYQs	Practice questions
Moment of Inertia	12	103
Dynamics of Rotational Motion about a Fixed Axis	9	94
Angular Momentum in Case of Rotation about a Fixed Axis	5	45
Centre of Mass	3	72
Kinematics of Rotational Motion about a Fixed Axis	3	34
Equilibrium of a Rigid Body	3	22
Torque and Angular Momentum	2	76
Angular Velocity and Its Relation with Linear Velocity, Angular Acceleration	2	20
Linear Momentum of a System of Particles	1	12
Motion of Centre of Mass	0	36
Miscellaneous Examples	0	1

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System of Particles and Rotational Motion: NEET PYQs and weightage

System of Particles and Rotational Motion: formula sheet for NEET

Torque

Newton's 2nd law for rotation

Moment of inertia

Standard I values

Parallel axis theorem

Rotational KE

Angular momentum

Torque and angular momentum

Conservation of angular momentum

Rotational kinematics

Linear and angular link

Work and power by a torque

Centre of mass

KE of a system

How does NEET ask System of Particles and Rotational Motion?

Which topics in System of Particles and Rotational Motion carry the most questions?

Why does System of Particles and Rotational Motion show "–" until you answer 3 questions?

What happens when you test System of Particles and Rotational Motion?

Chapters either side of System of Particles and Rotational Motion by weight