Mechanical Rotation Objective Questions and Answers - Set 04 - ObjectiveBooks

# Practice Test: Question Set - 04

1. A wheel starts from rest and has an angular acceleration of 4.0 rad/s². The time it takes to make 10 revolutions is:
(A) 0.50 sec
(B) 0.71 sec
(C) 2.2 sec
(D) 5.6 sec

2. A rod is pivoted about its center. A 5-N force is applied 4 m from the pivot and another 5-N force is applied 2 m from the pivot, as shown. The magnitude of the total torque about the pivot (in N.m) is:
(A) 0
(B) 5
(C) 8.7
(D) 15

3. A car travels north at constant velocity. It goes over a piece of mud which sticks to the tire. The initial acceleration of the mud, as it leaves the ground, is:
(A) Vertically upward
(B) Horizontally to the north
(C) Horizontally to the south
(D) Zero

4. A 0.70-kg disk with a rotational inertia given by MR2/2 is free to rotate on a fixed horizontal axis suspended from the ceiling. A string is wrapped around the disk and a 2.0-kg mass hangs from the free end. If the string does not slip then as the mass falls and the cylinder rotates the suspension holding the cylinder pulls up on the cylinder with a force of:
(A) 6.9 N
(B) 9.8 N
(C) 16 N
(D) 26 N

5. The angular speed in rad/sec of the minute hand of a watch is:
(A) 60/π
(B) 1800/π
(C) π
(D) π/1800

6. A wheel initially has an angular velocity of 18 rad/sec but it is slowing at a rate of 2.0 rad/s2. The time it takes to stop is:
(A) 3.0 sec
(B) 6.0 sec
(C) 9.0 sec
(D) 12 sec

7. The angular velocity vector of a spinning body points out of the page. If the angular acceleration vector points into the page then:
(A) The body is slowing down
(B) The body is speeding up
(C) The body is starting to turn in the opposite direction
(D) The axis of rotation is changing orientation

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

9. Consider four objects, each having the same mass and the same radius:

1. A solid sphere

2. A hollow sphere

3. A flat disk in the x, y plane

4. A hoop in the x, y plane

The order of increasing rotational inertia about an axis through the center of mass and parallel to the z axis is:

(A) 1, 2, 3, 4
(B) 4, 3, 2, 1
(C) 1, 3, 2, 4
(D) 4, 2, 3, 1

10. A disk is free to rotate on a fixed axis. A force of given magnitude F, in the plane of the disk, is to be applied. Of the following alternatives the greatest angular acceleration is obtained if the force is:
(A) Applied tangentially halfway between the axis and the rim
(B) Applied tangentially at the rim
(C) Applied radially halfway between the axis and the rim
(D) Applied radially at the rim

11. A phonograph turntable, rotating at 0.75 rev/sec, slows down and stops in 30 sec. The magnitude of its average angular acceleration in rad/s2 for this process is:
(A) 1.5
(B) 1.5π
(C) π/40
(D) π/20

12. If the angular velocity vector of a spinning body points out of the page then, when viewed from above the page, the body is spinning:
(A) Clockwise about an axis that is perpendicular to the page
(B) Counterclockwise about an axis that is perpendicular to the page
(C) About an axis that is parallel to the page
(D) About an axis that is changing orientation

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

14. A solid cylinder made of lead has the same mass and the same length as a solid cylinder made of wood. The rotational inertia of the lead cylinder compared to the wooden one is:
(A) Greater
(B) Less
(C) Same
(D) Unknown unless the radii are given

15. A block is attached to each end of a rope that passes over a pulley suspended from the ceiling. The blocks do not have the same mass. If the rope does not slip on the pulley, then at any instant after the blocks start moving the rope:
(A) Pulls on both blocks, but exerts a greater force on the heavier block
(B) Pulls on both blocks, but exerts a greater force on the lighter block
(C) Pulls on both blocks and exerts the same non-zero force on both
(D) Does not pull on either block

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