PHY 317K
October 12, 2006
HOMEWORK # 4
DUE on October 30, 2006 by 8:00pm
Instructions:
Use a SCANTRON ANSWER SHEET to mark answers. Provide your NAME (last,
first), UT EID, and UNIQUE NUMBER of the course. Sign and date it. The answer sheets must be
placed in the 317K box (by bulletin board outside PAI 2.48) by 8:00pm on Monday, October 30,
2006.
Late homework will not be graded.
Answer the following 56 questions:
1. A radian is about:
A) 25
°
B) 37
°
C) 45
°
D) 57
°
E) 90
°
2. One revolution per minute is about:
3. If a wheel turning at a constant rate completes 100 revolutions in 10 s its angular speed is:
4. A flywheel, is initially rotating at 20 rad/s and has a constant angular acceleration. After
9.0 s it has rotated through 450 rad. Its angular acceleration is:
A) 3.3 rad/s
2
B) 4.4 rad/s
2
C) 5.6 rad/s
2
D) 6.7 rad/s
2
E) 11 rad/s
2
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5. A flywheel rotating at 12 rev/s is brought to rest in 6 s. The magnitude of the average
angular acceleration in rad/s
2
of the wheel during this process is:
6. A wheel initially has an angular velocity of 36 rad/s but after 6.0s its angular velocity is 24
rad/s. If its angular acceleration is constant the value is:
A) 2.0 rad/s
2
B) –2.0 rad/s
2
C) 3.0 rad/s
2
D) –3.0 rad/s
2
E) 6.0 rad/s
2
7. A wheel starts from rest and has an angular acceleration that is given by
α
(
t
) = (6
rad/s
4
)t
2.
The angle through which it turns in time
t
is given by:
A) [(1/8)
t
4
] rad
B) [(1/4)
t
4
] rad
C) [(1/2)
t
4
] rad
D) (
t
4
) rad
E) 12 rad
8. The angular velocity vector of a spinning body points out of the page. If the angular
acceleration vector points into the page then:
9. For a wheel spinning with constant angular acceleration on an axis through its center, the
ratio of the speed of a point on the outer rim to the speed of a point halfway between the
center and the rim is:
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10. Four identical particles, each with mass
m
, are arranged in the
x
,
y
plane as shown. They
are connected by light sticks to form a rigid body. If
m
= 2.0 kg and
a
= 1.0 m, the
rotational inertia of this array about the
y
-axis is:

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