Systems of Particles and Rotational Motion Test

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Systems of Particles and Rotational Motion Test - 71

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Question 1
4 / -1

A uniform rod AB of length l and mass m is free to rotate about point A. The rod is released from rest in horizontal position. Given that the moment of inertia of the rod about A is ml²/3 the initial angular acceleration of the rod will be

A

B

C

D

Solution
Question 2
4 / -1

A ladder rests against a frictionless vertical wall, with its upper end 6 m above the ground and the lower end 4 m away from the wall. The weight of the ladder is 500 N and its C. G. at 1/3 rd distance from the lower end. Wall\'s reactions will be, (in newton)

A
111

B
333

C
222

D
129
Question 3
4 / -1

A constant torque of 31.4 N-m is exerted on a pivoted wheel. If angular acceleration of wheel is 4π rad/sec², then the moment of inertia of the wheel is

A
2.5 kg-m²

B
3.5 kg-m²

C
4.5 kg-m²

D
5.5 kg-m²

Solution
Question 4
4 / -1

A string is wound round the rim of a mounted flywheel of mass 20 kg and radius 20 cm. A steady pull of 25 N is applied on the cord. Neglecting friction and mass of the string, the angular acceleration of the wheel is

A
50 s^-2

B
25 s^-2

C
12.5 s^-2

D
6.25 s^-2

Solution
Question 5
4 / -1

A thin circular ring of mass M and radius r is rotating about its axis with a constant angular velocity ω. Four objects each of mass m, are kept gently to the opposite ends of two perpendicular diameters of the ring. The angular velocity of the ring will be

A

B

C

D

Solution
Question 6
4 / -1

A 2 kg mass is rotating on a circular path of radius 0.8 m with angular velocity of 44 rad/sec. If radius of path becomes lm, then the value of angular velocity will be

A
28.16 rad/sec

B
35.16 rad/sec

C
19.28 rad/sec

D
8.12 rad/sec

Solution
Question 7
4 / -1

The angular momentum of a system of particles is conserved

A
When no external force acts upon the system

B
When no external torque acts on the system

C
When no external impulse acts upon the system

D
When axis of rotation remains same
Question 8
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 stretched her arms fully, the spinning speed decreases in 10 rad/s. If I is the initial moment of inertia of the dancer, the new moment of inertia is

A
2I

B
3I

C
I/2

D
I/3

Solution
Question 9
4 / -1

A uniform heavy disc is rotating at constant angular velocity ω about a vertical axis through its centre and perpendicular to the plane of the disc. Let L be its angular momentum. A lump of plasticine is dropped vertically on the disc and sticks to it. which will be constant?

A
ω

B
ω and L both

C
L only

D
Neither ω nor L
Question 10
4 / -1

A particle of mass m is rotating in a plane in circular path of radius r. Its angular momentum is L. The centripetal force acting on the particle is

A
L²/mr

B
L²m /r

C
L²/m²r²

D
L² / mr³

Solution