Rotational Motion NCERT Based MCQ Questions for NEET

This article contains NCERT based 45 MCQ questions test on Physics chapter "Rotational Motion". These questions are highly valuable for the NEET exam. You can attempt these questions in the form of an interactive quiz and calculate your score. Read the below quiz rules carefully before you start

General Instructions

• Quiz contains 45 questions of 4 marks each.
• Correct answer (✔) will award you +4 marks and Incorrect answer (✘) will give you -1 mark.
• Total test is of 180 marks.
• Tap on box in order to select any option that you think is correct.
• Press the Submit button given in the end of quiz to calculate your score.
• There is a PDF file attached in the end of quiz. You can see detailed solutions to all questions and do self analysis from that file as well. 

Question 1. Find out the moment of inertia of the following structure (written as (PHYSICS) about axis AB made of thin uniform rods of mass per unit length λ. [Assume the upper arms of ‘Y’ are perpendicular to the axis. The length of each arm = l]

(1) 13 λ l³

(2) 10 λ l³

(3) 7 λ l³

(4) 11 λ l³

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Question 2. A wheel starting from rest, is rotating with a constant angular acceleration of 3.0 rad/sec². An observer notes that it traces an angle of 120 radian in 4.0 sec interval. For how long the wheel had been rotated when the observer started his observation?

(1) 4 sec

(2) 2 sec

(3) 8 sec

(4) 6 sec

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Question 3. The shaft of an eletric motor starts from rest and on the application of a torque, it gains an angular acceleration given by α = 3t – t² , during the first 2seconds. The angular velocity after 6 seconds will be-

(1) 10/3 rad/sec

(2) 20/3 rad/sec

(3) 5/3 rad/sec

(4) 1/3 rad/sec

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Question 4. A particle falls freely near the surface of the earth. Consider a fixed point O (not vertically) below the particle on the ground. Then pickup the INCORRECT alternative –

(1) Angular momentum of the particle about O is increasing.

(2) Torque of the gravitational force on the particle about O is decreasing.

(3) The moment of inertia of the particle about O is decreasing.

(4) The angular velocity of the particle about O is increasing.

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Question 5. A mass of 2 kg is rotating on a circular path of radius 0.8 m with angular velocity of 44 rad/s. If the radius of the path becomes 1.0 m, what will be the value of angular velocity ?

(1) 2.816 rad/sec

(2) 3.832 rad/sec

(3) 5.899 rad/sec

(4) 28.16 rad/sec

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Question 6. Following objects each having same mass and same radius are rotated about their respective self axes. Which will have greatest angular acceleration if same tangential force is applied on each –

(1) Disc

(2) Ring

(3) Solid sphere

(4) Hollow sphere

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Question 7. A uniform rod of mass M and length L is horizontally suspended from the ceiling by two vertical light cables as shown. Cable A is connected 1/4 th distance from the left end. Cable B is attached at right end. What is the tension in cable A – 

(1) Mg/4

(2) Mg/3

(3) 2Mg/3

(4) 3 Mg/4

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Question 8. In the figure shown, a cubical block is held stationary against a rough wall by applying a force 'F' then incorrect statement among the following is –

(1) Frictional force, f = Mg

(2) F = N, N is normal reaction

(3) F does not apply any torque

(4) N does not apply any torque

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Question 9. A bob of mass m attached to an inextensible string of length l is suspended from a vertical support. The bob rotates in a horizontal circle with an angular speed ω rad/s about the vertical. About the point of suspension : 

 (1) Angular momentum changes in direction but not in magnitude. 

 (2) Angular momentum changes both in direction and magnitude. 

 (3) Angular momentum is conserved. 

 (4) Angular momentum changes in magnitude but not in direction. 

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Question 10. A mass ‘m’ is supported by a massless string wound around a uniform hollow cylinder of mass m and radius R. If the string does not slip on the cylinder, with what acceleration will the mass fall on release? 

(1) 5g/6

(2) g

(3) 2g/3

(4) g/2

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Question 11. In the figure, shown a ball rolls without sliding, on a horizontal surface. It ascends a curved track upto height h and returns. Value of h is h1 for sufficiently rough curved track to avoid sliding and h2 for smooth curved track, then –

(1) h₁ = h₂

(2) h₁ < h₂

(3) h₁ > h₂

(4) h₁ = 2 h₂

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Question 12. A body of mass m slides down an incline and reaches the bottom with a velocity v. If the same mass were in the form of a ring, which rolls down this incline, the velocity of the ring at bottom would have been-

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Question 13. Three spheres of mass M and radius R are arranged as shown in figure. Then moment of inertia of system about axis YY' will be –

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Question 14. A disc of mass M and radius R rolls on a horizontal surface and then rolls up an inclined plane as shown in the figure. If the velocity of the disc is v, the height h to which the disc will rise on the inclined will be –

(1) 4v²/3g

(2) 4v²/g

(3) 3v²/2g

(4) 3v²/4g

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Question 15. Distance of the centre of mass of a solid uniform cone from its vertex is zo. If the radius of its base is R and its height h, then z_o is equal to

(1) 3h / 4

(2) 5h / 8

(3) 3h² / 8R

(4) h² / 4R

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Question 16. From a solid sphere of mass M and radius R a cube of maximum possible volume is cut. Moment of inertia of cube about an axis passing through its center and perpendicular to one of its faces is

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Question 17. A solid sphere, a hollow sphere and a ring are released from top of an inclined plane (frictionless) so that they slide down the plane. Then maximum acceleration down the plane is for (no rolling)

(1) Solid sphere

(2) Hollow-sphere

(3) Ring

(4) All same

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Question 18. Moment of inertia of a circular wire of mass M and radius R about its diameter is –

(1) MR²

(2) MR²/2

(3) 2 MR²

(4) MR²/4 

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Question 19. A circular disc X of radius R is made from an iron plate of thickness t and another disc Y of radius 4R is made from an iron plate of thickness t/4. Then the relation between the moment of inertia I_X and I_Y is –

(1) I_Y = 16 I_X 

(2) I_Y = I_X

(3) I_Y = 64 I_X 

(4) I_Y = 32 I_X 

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Question 20. A particle performing uniform circular motion has angular momentum L. If its angular frequency is doubled and its kinetic energy halved, then the new angular momentum is

(1) 2 L 

(2) 4 L

(3) L / 2 

(4) L / 4 

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Question 21. A solid sphere is rotating in free space. If the radius of the sphere is increased keeping mass same which one of the following will not be affected ?

(1) Moment of inertia

(2) Angular momentum

(3) Angular velocity

(4) Rotational kinetic energy

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Question 22. One solid sphere A and another hollow sphere B are of same mass and same radii. Their

moment of inertia about their diameters are respectively I_A and I_B such that

(1) I_A = I_B 

(2) I_A > I_B

(3) I_A < I_B 

(4) I_A/I_B = d_A/d_B

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Question 23. An annular ring with inner and outer radii R₁ and R₂ is rolling without slipping with a uniform angular speed. The ratio of the forces experienced by the two particles situated on the inner and outer parts of the ring, F₁/F₂ is –

(1) R₂/R₁ 

(2) (R₁/R₂)²

(3) 1 

(4) R₁/R₂

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Question 24. The moment of inertia of uniform semicircular disc of mass M and radius r about a line perpendicular to the plane of the disc through the centre is

(1) (1/4) Mr² 

(2) (2/5) Mr²

(3) Mr² (4) 

(1/2) Mr²

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Question 25. A 'T' shaped object with dimensions shown in the figure, is lying on a smooth floor. A force F is applied at the point P parallel to AB, such that the object has only the translational motion without rotation. Find the location of P with respect to C.

(1) 2l / 3

(2) 3l / 2

(3) 4l / 3 

(4) l

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Question 26. The density of a non-uniform rod of length 1m is given by p(x) = a (1 + bx²), where a and b are constants and 0 ≤ x ≤ 1. The centre of mass of the rod will be at –

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Question 27. A force of – F k̂ acts on O, the origin of the coordinate system. The torque about the point

(1, – 1) is – 

(1) F (î + ĵ) 

(2) – F (î − ĵ)

(3) F (î − ĵ) 

(4) – F (î + ĵ) 

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Question 28. Four point masses, each of value m, are placed at the corners of a square ABCD of side l. The moment of inertia of this system about an axis passing through A and parallel to BD is

(1) 3 ml² 

(2) ml²

(3) 2 ml² 

(4) √3 ml²

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Question 29. For the given uniform square lamina ABCD, whose centre is O, 

(1) √2 I_AC = I_EF 

(2) I_AD = 3I_EF

(3) I_AC = I_EF 

(4) I_AC = √2 I_EF

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Question 30. Two blocks of masses 10 kg and 4 kg are connected by a spring of negligible mass and

placed on a frictionless horizontal surface. An impulse gives a velocity of 14 m/s to the heavier block in the direction of the lighter block. The velocity of the centre of mass is :

(1) 30 m/s 

(2) 20 m/s

(3) 10 m/s 

(4) 5 m/s

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Question 31. A round uniform body of radius R, mass M and moment of inertia ‘I’, rolls down (without

slipping) an inclined plane making an angle θ with the horizontal. Then its acceleration is

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Question 32. Angular momentum of the particle rotating under the influence of a central force is constant due to –

(1) Constant force

(2) Constant linear momentum

(3) Zero torque

(4) Constant torque

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Question 33. Consider a uniform square plate of side ‘a’ and mass ‘m’. The moment of inertia of this plate about an axis perpendicular to its plane and passing through one of its corners is

(1) 1/12 ma²

(2) 7/12 ma²

(3) 2/3 ma²

(4) 5/6 ma²

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Question 34. A thin uniform rod of length l and mass m is swinging freely about a horizontal axis passing through its end. Its maximum angular speed is ω. Its centre of mass rises to a maximum height of -

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Question 35. 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 –

(1) remains unchanged

(2) continuously decreases

(3) continuously increases

(4) first increases and then decreases

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Question 36. A pulley of radius 2m is rotated about its axis by a force F = (20t – 5t²) newton (where t is

measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m², the number of rotations made by the pulley before its direction of motion is reversed, is :

(1) less than 3

(2) more than 3 but less than 6

(3) more than 6 but less than 9

(4) more than 9

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Question 37. Adiatomic molecule is made of two masses m₁ and m₂ which are separated by a distance r. If we calculate its rotational energy by applying Bohr’s rule of angular momentum quantization, its energy will be given by – (n is an integer)

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Question 38. A hoop of radius r and mass m rotating with an angular velocity ωₒ is placed on a rough horizontal surface. The initial velocity of the centre of the hoop is zero. What will be the velocity of the centre of the hoop when it ceases to slip?

(1) rωₒ/2 

(2) rωₒ/3

(3) rωₒ/2 

(4) rωₒ

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Question 39. Two bodies have their moments of inertia I and 2I respectively about their axis of rotation. If their kinetic energies of rotation are equal, their angular momenta will be in the ratio –

(1) 2 : 1 

(2) 1 : 2

(3) √2 :1 

(4) 1: √2

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Question 40. A drum of radius R and mass M, rolls down without slipping along an inclined plane of angle θ. The frictional force –

(1) Dissipates energy as heat

(2) Decreases the rotational motion

(3) Decreases the rotational and translational motion

(4) Converts translational energy to rotational energy

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Question 41. The moment of inertia of a uniform circular disc of radius R and mass M about an axis touching the disc at its diameter and normal to the disc is –

(1) 2 MR² / 5

(2) 3 MR² / 2

(3) MR² / 2

(4) MR²

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Question 42. A uniform rod of length l and mass m is free to rotate in a vertical plane about A. The rod initially in horizontal position is released. The initial angular acceleration of the rod is (Moment of inertia of rod about A is ml²/3)

(1) 2l/3g

(2) 3g/2l²

(3) mgl/2

(4) 3g/2l

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Question 43. A particle of mass m moves in the XY plane with a velocity v along the straight line AB. If the angular momentum of the particle with respect to origin O is L_A when it is at A and L_B when it is at B, then –

(1) L_A = L_B

(2) the relationship between L_A and L_B depends upon the slope of the line AB

(3) L_A < L_B

(4) L_A > L_B

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Question 44. A wheel has angular acceleration of 3.0 rad/sec² and an initial angular speed of 2.00 rad/sec. In a time of 2 sec it has rotated through an angle (in radian) of –

(1) 10 

(2) 12

(3) 4 

(4) 6

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Question 45. The ratio of the radii of gyration of a circular disc to that of a circular ring, each of same mass and radius, around their respective axes is

(1) √2 : √3 

(2) √3 : √2

(3) 1 : √2 

(4) √2 :1

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Detailed Solutions

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