# 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**

*MR*^{2}/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/

*Ï€*

- (B) 1800/

*Ï€*

- (C)

*Ï€*

- (D)

*Ï€*/1800

**6. A wheel initially has an angular velocity of 18 rad/sec but it is slowing at a rate of 2.0 rad/s**

^{2}. 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/s**

^{2}for this process is:- (A) 1.5

- (B) 1.5

*Ï€*

- (C)

*Ï€*/40

- (D)

*Ï€*/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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