Mechanical Rotation Design Questions & Answers - Set 01 - ObjectiveBooks
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# Practice Test: Question Set - 01

1. ‘A’ and ‘B’ are two solid cylinders made of aluminum. Their dimensions are shown. The ratio of the rotational inertia of B to that of ‘A’ about the common axis X-X' is:
(A) 2
(B) 4
(C) 8
(D) 32

2. A disk starts from rest and rotates about a fixed axis, subject to a constant net torque. The work done by the torque during the second revolution is _________ as the work done during the first revolution.
(A) The same
(B) Twice as much
(C) Half as much
(D) Four times as much

3. A wheel rotates with a constant angular acceleration of π rad/s². During the time interval from t1 to t2 its angular displacement is π rad. At time t2 its angular velocity is 2π rad/sec. Its angular velocity in rad/s at time t1 is:
(A) Zero
(B) 1
(C) π
(D) π/√2

4. A wheel initially has an angular velocity of -36 rad/sec but after 6.0 sec its angular velocity is -24 rad/sec. If its angular acceleration is constant the value is:

5. A child, riding on a large merry-go-round, travels a distance of 3000 m in a circle of diameter 40 m. The total angle in radians through which she revolves is:
(A) 50
(B) 75
(C) 150
(D) None of these

6. For a wheel spinning on an axis through its center, the ratio of the tangential acceleration of a point on the rim to the tangential acceleration of a point halfway between the center and the rim is:
(A) 1
(B) 2
(C) 1/2
(D) 4

7. Three identical balls are tied by light strings to the same rod and rotate around it, as shown below. Rank the balls according to their rotational inertia, least to greatest.
(A) 1, 2, 3
(B) 3, 2, 1
(C) 3, then 1 and 2 tie
(D) 1, 3, 2

8. The rotational inertia of a disk about its axis is 0.70 kg.m2. When a 2.0 kg weight is added to its rim, 0.40 m from the axis, the rotational inertia becomes:
(A) 0.38 kg.m2
(B) 0.54 kg.m2
(C) 0.70 kg.m2
(D) 1.0 kg.m2

9. One revolution is about the same as:

10. A disk with a rotational inertia of 5.0 kg.m2 and a radius of 0.25 m rotates on a frictionless fixed axis perpendicular to the disk and through its center. A force of 8.0 N is applied tangentially to the rim. The angular acceleration of the disk is:

11. A 16 kg block is attached to a cord that is wrapped around the rim of a flywheel of diameter 0.40 m and hangs vertically, as shown. The rotational inertia of the flywheel is 0.50 kgm2. When the block is released and the cord unwinds, the acceleration of the block is:
(A) 0.15 g
(B) 0.56 g
(C) 0.84 g
(D) 100 g

12. A 8.0-cm radius disk with a rotational inertia of 0.12 kgm2 is free to rotate on a horizontal axis. A string is fastened to the surface of the disk and a 10-kg mass hangs from the other end. The mass is raised by using a crank to apply a 9.0-Nm torque to the disk. The acceleration of the mass is:
(A) 0.50 m/s2
(B) 1.7 m/s2
(C) 6.2 m/s2
(D) 12 m/s2

13. A pulley with a radius of 3.0 cm and a rotational inertia of 4.5 × 10-3 kgm2 is suspended from the ceiling. A rope passes over it with a 2.0-kg block attached to one end and a 4.0-kg block attached to the other. The rope does not slip on the pulley. At any instant after the blocks start moving the object with the greatest kinetic energy is:
(A) The heavier block
(B) The lighter block
(C) The pulley
(D) Either block (the two blocks have the same kinetic energy)

14. If a wheel turns with constant angular speed then:
(A) Each point on its rim moves with constant velocity
(B) Each point on its rim moves with constant acceleration
(C) The wheel turns through equal angles in equal times
(D) The angle through which the wheel turns in each second increases as time goes on

15. A flywheel, initially at rest, has a constant angular acceleration. After 9 s the flywheel has rotated 450 rad. Its angular acceleration in rad/sec2 is:
(A) 100
(B) 1.77
(C) 50
(D) 11.1

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