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JEE • PHYSICS • SYSTEM OF PARTICLES

System of particles practice · Mixed difficulty

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Practice format and chapter quiz

These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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Showing 1-30 of 483 questions

1 Medium

1 of 483

Understanding +4 | -1

It is easier for a swimmer jumping into water from a height to describe a loop in the air by

View answer and explanation

Correct option: C

keeping the arms and legs straight

Option A is correct. Pulling the arms and legs closer decreases the moment of inertia, which increases the angular velocity, making it easier to perform a loop.

2 Medium

2 of 483

Application +4 | -1

A uniform thin rod

\mathrm{AB}

of length

\mathrm{L}

has linear mass density

\mu(x)=a+\frac{b x}{L}

, where

x

is measured from

\mathrm{A}

. If the

\mathrm{CM}

of the rod lies at a distance of

\left(\frac{7}{12}\right) \mathrm{L}

from

\mathrm{A}

, then a and

\mathrm{b}

are related as :

View answer and explanation

Correct option: B

2 a=b

Option B (

2 a=b

) is correct because it represents the relationship between a and b derived from the center of mass calculation.

3 Medium

3 of 483

Application +4 | -1

A solid metal ring and a disc of same radius and mass are rotating about their diameters with same angular frequency. The ratio of their respective rotational kinetic energy values is

View answer and explanation

Correct option: C

2: 1

Option C (

2: 1

) is correct because the rotational kinetic energy depends on the moment of inertia, which differs for a ring and a disc of the same mass and radius.

4 Medium

4 of 483

Understanding +4 | -1

When a torque acting upon a system is zero, then which of the following will be constant

View answer and explanation

Correct option: C

Angular momentum

Option C is correct. When the net torque acting on a system is zero, the angular momentum of the system is conserved (constant).

5 Medium

5 of 483

Application +4 | -1

A point particle of mass

1.0 \mathrm{~g}

is rotating in a circle of diameter

8 \mathrm{~cm}

. Its moment of inertia will be

View answer and explanation

Correct option: D

16 \mathrm{~g}-\mathrm{cm}^2

Option D (

16 \mathrm{~g}-\mathrm{cm}^2

) is correct because the moment of inertia of a point particle is calculated using the formula

I = MR^2

6 Easy

6 of 483

Application +4 | -1

The angular velocity of a particle is given by

\omega = {t^4} + 2{t^3}

then its angular acceleration of the particle at

t = 1\,sec

\left( {rad\,{s^{ - 2}}} \right)

View answer and explanation

Correct option: C

Option C (10) is correct because the angular acceleration is the derivative of the angular velocity with respect to time, and evaluating the derivative at t=1 sec gives 10 rad/s².

7 Medium

7 of 483

Analyzing +4 | -1

Assertion: The reference frame does not decide the position of centre of mass.
Reason: Centre of mass depends only upon the rest mass of the body.

View answer and explanation

Correct option: C

If assertion is true but reason is false

Option C is correct. The assertion is true because the center of mass position is independent of the reference frame. The reason is false because the center of mass depends on the mass distribution, not just the rest mass.

8 Medium

8 of 483

Understanding +4 | -1

If the torque acting on a rigid body, under the application of a force, is zero then it's

View answer and explanation

Correct option: D

Angular momentum is conserved

Option D (Angular momentum is conserved) is correct because if the net torque acting on a rigid body is zero, its angular momentum remains constant (conserved).

9 Medium

9 of 483

Understanding +4 | -1

A body A of mass M while falling vertically downwards under gravity breaks into two parts; a body B of mass

\frac{1}{3}M

and a body C of mass

\frac{2}{3}M

. The centre of mass of bodies B and C taken together shifts compared to that of body A towards

View answer and explanation

Correct option: B

Does not shift

Option B (Does not shift) is correct because the acceleration of the center of mass remains the same (g) after the break, so there's no shift.

10 Medium

10 of 483

Understanding +4 | -1

Which of the following type of wheels of same mass and radius will have largest moment of inertia?

View answer and explanation

Correct option: A

Ring

Option A is correct because a ring has its mass distributed farthest from the axis of rotation, resulting in the largest moment of inertia.

11 Medium

11 of 483

Understanding +4 | -1

Assertion: Angular momentum may not necessarily be parallel to angular velocity vector.
Reason: The body may not be symmetrical about its axis of rotation.

View answer and explanation

Correct option: A

If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion

Option A (If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion) is correct because angular momentum is not always parallel to angular velocity, and this is due to the body not being symmetrical about its axis of rotation.

12 Medium

12 of 483

Application +4 | -1

A ballet dancer, dancing on a smooth floor is spinning about a vertical axis with her arms folded with an angular velocity of

20\;rad/s

. When she stretches her arms fully, the spinning speed decrease in

10\;rad/s

. If I is the initial moment of inertia of the dancer, the new moment of inertia is

View answer and explanation

Correct option: A

2\,I

Option A (

2\,I

) is correct because angular momentum is conserved, and when the angular velocity halves, the moment of inertia doubles.

13 Medium

13 of 483

Analyzing +4 | -1

A thin horizontal circular disc is rotating about a vertical axis passing through its centre. An insect is at rest at a point near the rim of the disc. The insect now moves along a diameter of the disc to reach its other end. During the journey of the insect, the angular speed of the disc

View answer and explanation

Correct option: C

first increases and then decreases

The correct answer is C (first increases and then decreases) because the moment of inertia changes as the insect moves, affecting the angular speed due to conservation of angular momentum.

14 Medium

14 of 483

Application +4 | -1

A constant torque acting on a uniform circular wheel changes its angular momentum from

{1\mathrm{~A}}_0

5 \mathrm{~A}_0

to in 6 seconds, Then the magnitude of torque is -

View answer and explanation

Correct option: A

\frac{2}{3} \mathrm{~A}_0

Option A (

\frac{2}{3} \mathrm{~A}_0

) is correct because torque is the rate of change of angular momentum, which is (5A0 - A0)/6.

15 Medium

15 of 483

Understanding +4 | -1

Assertion: The moment of inertia of a body depends on the manner, in which mass is distributed about the axis of rotation.
Reason: Moment of inertia of a body will be more, if heavier mass is distributed away from the axis of rotation and lighter mass near it.

View answer and explanation

Correct option: A

If both assertion and reason are true and reason is the correct explanation of the assertion

Option A (If both assertion and reason are true and reason is the correct explanation of the assertion) is correct because the moment of inertia depends on the mass distribution, and distributing heavier mass further from the axis increases it.

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16 Medium

16 of 483

Remembering +4 | -1

The moment of inertia

(I)

and the angular momentum

(L)

are related by the expression

View answer and explanation

Correct option: B

L=I \omega

Option B (

L=I \omega

) is correct because the angular momentum (L) is the product of the moment of inertia (I) and the angular velocity (

\omega

17 Medium

17 of 483

Application +4 | -1

The moment of inertia of a uniform rod about a perpendicular axis passing through one end is

{I_1}

. The same rod is bent into a ring and its moment of inertia about a diameter is

{I_2}

. Then

\frac{{{I_1}}}{{{I_2}}}

View answer and explanation

Correct option: D

\frac{{8{\pi ^2}}}{3}

The correct answer is D (

\frac{{8{\pi ^2}}}{3}

) because the ratio of the moment of inertia of a rod about one end to the moment of inertia of a ring about its diameter is

\frac{{{I_1}}}{{{I_2}}} = \frac{{8{\pi ^2}}}{3}

18 Medium

18 of 483

Understanding +4 | -1

Total angular momentum of a rotating body remains constant, if the net torque acting on the body is :

View answer and explanation

Correct option: A

zero

Option A (zero) is correct because angular momentum is conserved when the net external torque acting on the system is zero.

19 Medium

19 of 483

Understanding +4 | -1

Assertion: Torque on a body may be non-zero even if net force acting on it is zero.
Reason: Force does not depend on point of application, but torque depends on point of application.

View answer and explanation

Correct option: A

If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion

Option A (If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion) is correct because a net force of zero doesn't preclude a non-zero torque, as torque depends on the point of application of forces.

20 Medium

20 of 483

Understanding +4 | -1

The moment of inertia of a ___A___ body about an axis ___B___ to its plane is equal to the sum of its moments of inertia about two ___C___ axes concurrent with perpendicular axis and lying in the plane of the body. Here, A, B, and C refer to:

View answer and explanation

Correct option: C

Planar, perpendicular, and perpendicular

Option C (Planar, perpendicular, and perpendicular) is correct because it accurately describes the perpendicular axis theorem for planar bodies.

21 Medium

21 of 483

Analyzing +4 | -1

Assertion: When you lean behind over the hind legs of the chair, the chair falls back after a certain angle.

Reason: Centre of mass lying outside the system makes the system unstable.

View answer and explanation

Correct option: C

If Assertion is correct but Reason is incorrect.

Option C is correct. The chair falls because the center of mass shifts outside the base of support, causing instability. The reason is incorrect because stability depends on the position of the center of mass relative to the support base, not whether it's inside the system.

22 Medium

22 of 483

Application +4 | -1

A wheel of mass

20 \mathrm{~kg}

and radius

30 \mathrm{~cm}

is rotating at an angular speed of

80 \mathrm{~rev} / \mathrm{min}

when the motor is turned off. Neglecting the friction at the axis, calculate the force that must applied tangentially to the wheel to bring it to rest in 5 revolution.

View answer and explanation

Correct option: A

1.06\,\pi \mathrm{N}

Option A (

1.06\pi \mathrm{N}

) is correct because it is the tangential force required to bring the wheel to rest in 5 revolutions, calculated using rotational kinematics and torque.

23 Medium

23 of 483

Understanding +4 | -1

In an elastic head on collision between two particles

View answer and explanation

Correct option: A

Velocity of separation is equal to the velocity of approach

Option A (Velocity of separation is equal to the velocity of approach) is correct because, in an elastic collision, the coefficient of restitution (e) is 1, which means the velocity of separation equals the velocity of approach.

24 Medium

24 of 483

Analyzing +4 | -1

A rigid disc rolls without slipping on a fixed rough horizontal surface with uniform angular velocity. If the acceleration of lowest point on the disc

a

and the velocity of the lowest point on the disc is

v

, then

View answer and explanation

Correct option: C

a \neq 0, v=0

Option C is correct because at the lowest point, the velocity is instantaneously zero, but there's centripetal acceleration directed upwards.

25 Medium

25 of 483

Application +4 | -1

A dancer spins about himself with an angular speed

\omega

, with his arms extended. When he draws his hands in, his moment of inertia reduces by 40% . Then his angular velocity would be

View answer and explanation

Correct option: D

\frac{{5\omega }}{3}

Option D (

\frac{{5\omega}}{{3}}

) is correct because it is calculated using the conservation of angular momentum when the moment of inertia changes.

26 Medium

26 of 483

Understanding +4 | -1

Moment of inertia of a circular wire of mass

M

and radius

R

about is its diameter is:

View answer and explanation

Correct option: A

\frac{1}{2} {M} {R}^2

Option A (

\frac{1}{2} {M} {R}^2

) is correct because the moment of inertia about a diameter is half the moment of inertia about an axis perpendicular to the plane.

27 Medium

27 of 483

Application +4 | -1

The moment of inertia of a circular disc about one of its diameter is

I

. What will be its moment of inertia about a tangent parallel to the diameter?

View answer and explanation

Correct option: D

3I

Option D (

3I

) is correct because the moment of inertia about a tangent parallel to the diameter is calculated using the parallel axis theorem.

28 Medium

28 of 483

Analyzing +4 | -1

In a bicycle the radius of rear wheel is twice the radius of front wheel. If

{r_F}\,and\,{r_r}

are the radius,

{v_F}\,and\,{v_r}

, are speeds of top most points of wheel, then

View answer and explanation

Correct option: C

{v_F} = {v_r}

The correct answer is

{v_F} = {v_r}

because the speeds of the topmost points of the wheels are equal to twice the speed of the bicycle, which is the same for both wheels.

29 Medium

29 of 483

Application +4 | -1

The radius of a solid sphere is R and its density D. When it is made to rotate about an axis passing through any diameter of sphere, expression for its moment of inertia is

View answer and explanation

Correct option: B

\frac{8}{{15}}\mathrm{\pi D}{\mathrm{R}^5}

Option B (

\frac{8}{{15}}\mathrm{\pi D}{\mathrm{R}^5}

) is correct because it is derived from the formula for the moment of inertia of a solid sphere about its diameter.

30 Medium

30 of 483

Analyzing +4 | -1

An ant is sitting at the edge of a rotating disc. If the ant reaches the other end, after moving along the diameter, the angular velocity of the disc will

View answer and explanation

Correct option: C

First increases and then decreases

Option B (First decreases and then increases) is correct because the moment of inertia first decreases as the ant moves towards the center and then increases as it moves away, leading to corresponding changes in angular velocity to conserve angular momentum.

Revision notes and key takeaways

Review SYSTEM OF PARTICLES in your textbook or class notes, then use this set to check your understanding.

Key Takeaways

✓ This set contains 483 single-correct-answer MCQs on SYSTEM OF PARTICLES.
✓ Try each question before opening its answer. Read the explanation where one is available.
✓ Sign in to save submitted answers. Revisit incorrect answers alongside your textbook or class notes.

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