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Rotational Dynamics Class 12 MCQ

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Rotational Dynamics Class 12 MCQ. We covered all the Rotational Dynamics Class 12 MCQ in this post for free so that you can practice well for the exam.

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MCQ on Rotational Dynamics for NEET Students

Mechanical advantage is a concept based on

(A) moment of inertia

(B) principle of moments

(C) equilibrium of the rigid body

(D) parallel axis theorem

Option b – principle of moments

The statement; the angular acceleration is directly proportional to the applied torque and is inversely proportional to the moment of inertia of the body, can be called

(A) Newton’s second law of motion for rotating bodies.

(B) Newton’s second law of motion for a body rotating along the axis passing through its center.

(C) Newton’s second law of motion for a body rotating about a fixed axis.

(D) Newton’s second law of motion for a body rotating about an axis perpendicular to the plane of the body.

Option c – Newton’s second law of motion for a body rotating about a fixed axis.

A toy car placed on a rough table possesses

(A) no equilibrium

(B) translational equilibrium

(C) rotational equilibrium

(D) translational and rotational equilibrium

Option d – translational and rotational equilibrium

The total torque on a system is

(A) independent of origin.

(B) independent of origin if the total external force acting is zero.

(C) independent of origin if the total external force acting is constant.

(D) dependent of origin.

Option b – independent of origin if the total external force acting is zero.

When a body rolls without slipping,

(A) there is no work done against friction.

(B) there is positive work done against friction.

(C) there is negative work done against friction.

(D) work done depends on the sense of rolling.

Option a – there is no work done against friction.

A wheel of the moment of inertia 1 kg m² is rotating about at a speed of 90 rad/s. It comes to rest in 2 minutes due to friction. The angular momentum of the wheel a minute before it stops rotating is

(A) 90 kg m²/s

(B) 64 kg m²/s

(C) 51 kg m²/s

(D) 45 kg m²/s

Option d – 45 kg m²/s

Which of the following is not the rotational analog of force?

(A) Moment of force

(B) Impulse

(C) Torque

(D) Couple

Option b – Impulse

The ratio of the accelerations for a ring (mass m and radius R) rolling down an incline of angle ‘0’ without slipping and slipping down the incline without rolling is

(A) 1 : 2

(B) 2 : 3

(C) 2 : 5

(D) 2 : 1

Option a – 1 : 2

What should be the radius of a uniform cylinder of length 30 cm such that its moment of inertia about its perpendicular bisector should be minimum?

(A) 17.5 cm

(B) 24.5 cm

(C) 29.8 cm

(D) 31.2 cm

Option b – 24.5 cm

A rigid spherical body is spinning around an axis without any external torque. Due to changes in temperature, its volume increases by 2%. Its angular speed

(A) will increase approximately by 2%

(B) will decrease approximately by 2%

(C) will decrease approximately by 0.67 %

(D) will decrease approximately by 1.33%

Option d – will decrease approximately by 1.33%

If three particles A, B, and C are placed on the vertices of a triangle then the center of mass of a system

(A) will always be its geometric center.

(B) will never be its geometric center.

(C) will be its geometric center only if the triangle is equilateral.

(D) will be its geometric center if the triangle is equilateral and the particles are identical.

Option d – will be its geometric center if the triangle is equilateral and the particles are identical.

Choose an INCORRECT statement. For a spinning top,

(A) particles of the top lying on the axis of rotation of the top are stationary with respect to the spinning body of the top.

(B) point of contact of the top with the ground is fixed.

(C) its axis of rotation varies from time to time depending upon the cones it is sweeping in the space.

(D) its axis of rotation always passes through the point of contact with the ground.

Option c – its axis of rotation varies from time to time depending upon the cones it is sweeping in the space.

Assertion: For a very long pillar standing vertically, its center of gravity does not coincide with the center of mass. Reason: Centre of mass depends on the distribution of mass of the pillar.

(A) The assertion is True, Reason is True; Reason is a correct explanation for Assertion.

(B) The assertion is True, and Reason is True; Reason is not a correct explanation for Assertion.

(C) The assertion is True, Reason is False.

(D) The assertion is False, Reason is True.

Option b – The assertion is True, and Reason is True; Reason is not a correct explanation for Assertion.

A uniform wooden plank 4 m long and weighing 40 kg is resting on two supports 0.5 m from each end. A boy weighing 45 kg stands 1.5 m from one end of the wooden plank. What are the reactions to the support?

(A) 55 kg wt, 30 kg wt

(B) 45 kg wt, 40 kg wt

(C) 50 kg wt, 35 kg wt

(D) 63.7 kg wt, 21.3 kg wt

Option c – 50 kg wt, 35 kg wt

The moment of inertia of a ring about tangent in the plane of the ring as the axis of rotation

(A) 3 × M.I. of the ring along diameter as the axis of rotation.

(B) 1.5 M.I. of the ring along diameter as the axis of rotation.

(C) 3 × M.I. of ring about a line passing through its center and perpendicular to its plane as axis of rotation.

(D) 2 × M.I. of the ring along any tangent perpendicular to the plane of the ring as the axis of rotation.

Option a – 3 × M.I. of the ring along diameter as the axis of rotation.

A large value of the radius of gyration indicates ( Rotational Dynamics Class 12 MCQ )

(A) a large value of M.I. with mass distributed widely about an axis.

(B) a large value of M.I. with mass distributed widely away from the axis.

(C) a large value of M.I. with no information about mass distribution.

(D) a large value of M.I. and a large value of mass.

Option a – a large value of M.I. with mass distributed widely about an axis.

In pure translational motion at any instant of time, all particles of the body have the same velocity; the statement is true for

(A) an ice cube sliding across a floor.

(B) a steel beam sliding on an inclined plane.

(C) a pot getting shaped on a potter’s wheel.

(D) all of the above

Option b – a steel beam sliding on an inclined plane.

Which of the configuration’s positions of the center of mass coincides with their geometrical center?

(A) Uniform solid sphere

(B) Uniform rod

(C) Uniform circular ring

(D) all of the above

Option d – all of the above

The angular speed of the wheel is increased from 1200 rpm to 3600 rpm in 16 seconds such that it reaches 1600 rpm uniformly in 10 s and then uniformly reaches 3600 rpm, the ratio of angular accelerations observed respectively is

(A) 1:11

(B) 1:13

(C) 1:19

(D) 1:21

Option a – 1:11

For a body to possess only rotational motion, ( Rotational Dynamics Class 12 MCQ )

(A) the body should be balanced at its center of mass.

(B) the body should be balanced at its center of gravity.

(C) the body should be fixed along a line.

(D) the body should be rotated about an axis perpendicular to the plane of the body.

Option c – the body should be fixed along a line.

An engine of power 40 kW is installed on the rotor to attain a uniform angular speed of 200 rad/s. But the rotor is found to move with a uniform angular speed of 150 rad/s. What is the real power of machines?

(A) 50 kW

(B) 43 kW

(C) 30 kW

(D) 27 kW

Option c – 30 kW

Moment of inertia is a measure of (i) mass distribution of the body about the axis of rotation (ii) inertia of rotational motion of the body

(A) (i) only

(B) (ii) only

(C) (i) and (ii)

(D) (i) and (ii) for a uniform body

Option b – (ii) only

Assertion: Spokes are provided in a bicycle wheel. Reason: Mass of the bicycle wheel is less.

(A) The assertion is True, Reason is True; Reason is a correct explanation for Assertion.

(B) The assertion is True, and Reason is True; Reason is not a correct explanation for Assertion.

(C) The assertion is True, Reason is False.

(D) The assertion is False, Reason is True.

Option b – The assertion is True, and Reason is True; Reason is not a correct explanation for Assertion.

The radius of a solid sphere is 10 cm. The radius of gyration, when the axis of rotation is along a tangent, is

(A) 10 cm

(B) 11.8 cm

(C) 15 cm

(D) 14.3 cm

Option b – 11.8 cm

A flywheel attains an angular velocity of 32 rad/s from 4 rad/s in 7 s with constant angular acceleration. The total angle through which the flywheel has turned is

(A) 126 rad

(B) 98 rad

(C) 72 rad

(D) 24 rad

Option a – 126 rad

A massless cord is wound on the circular rim of the flywheel of mass 10 kg and radius 20 cm. When a cord is pulled steadily with 20 N unwinding 150 cm of cord, what is the K.E. of the wheel at this point? (Assume zero frictional loss)

(A) 17.8 J

(B) 20 J

(C) 23.8 J

(D) 30 J

Option d – 30 J

We covered all the rotational dynamics class 12 MCQ above in this post for free so that you can practice well for the exam.

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