Physics: Principles with Applications, Sixth Edition
47) A proton of mass 1.67 ˛ 10-27 kg rotates with an angular speed of 2 ˛ 106 rad/s in a circle of
radius 0.80 m in a cyclotron. What is the orbital angular momentum of the proton?
A) 1.28 ˛ 10-21 kgœm2/s
B) 1.76 ˛ 10-21 kgœm2/s
C) 2.14 ˛ 10-21 kgœm2/s
D) 3.20 ˛ 10-21 kgœm2/s
Answer: C
Diff: 2 Page Ref: Sec. 8.8
48) An ice skater has a moment of inertia of 5.0 kgœm2 when her arms are outstretched. At this
time she is spinning at 3.0 revolutions per second (rps). If she pulls in her arms and decreases
her moment of inertia to 2.0 kgœm2, how fast will she be spinning?
A) 2.0 rps
B) 3.3 rps
C) 7.5 rps
D) 10 rps
Answer: C
Diff: 1 Page Ref: Sec. 8.8
49) A figure skater rotating at 5.00 rad/s with arms extended has a moment of inertia of
2.25 kgœm2. If the arms are pulled in so the moment of inertia decreases to 1.80 kgœm2, what is
the final angular speed?
A) 2.25 rad/s
B) 4.60 rad/s
C) 6.25 rad/s
D) 0.81 rad/s
Answer: C
Diff: 2 Page Ref: Sec. 8.8
167
,Chapter 9 Static Equilibrium; Elasticity and Fracture
Conceptual Questions
1) What condition or conditions are necessary for rotational equilibrium?
A) SFx = 0
B) SFx = 0, ST = 0
C) ST = 0
D) SFx = 0, SFy = 0
Answer: C
Diff: 1 Page Ref: Sec. 9.1-9.2
2) What condition or conditions are necessary for static equilibrium?
A) SFx = 0
B) SFx = 0, SFy = 0, ST = 0
C) ST = 0
D) SFx = 0, SFy = 0
Answer: B
Diff: 1 Page Ref: Sec. 9.1-9.2
3) A book weighs 6 N. When held at rest above your head the net force on the book is
A) 0 N.
B) 6 N.
C) 9.8 N.
D) -6 N.
Answer: A
Diff: 1 Page Ref: Sec. 9.1-9.2
4) A rocket moves through outer space with a constant velocity of 9.8 m/s. What net force acts
on it?
A) a force equal to its weight on Earth, mg
B) a force equal to the gravity acting on it
C) The net force is zero.
D) cannot be determined without more information
Answer: C
Diff: 1 Page Ref: Sec. 9.1-9.2
168
, Physics: Principles with Applications, Sixth Edition
5) A person weighing 800 N stands with one foot on each of two bathroom scales. Which
statement is definitely true?
A) Each scale will read 800 N.
B) Each scale will read 400 N.
C) If one scale reads 500 N, the other will read 300 N.
D) None of the above is definitely true.
Answer: C
Diff: 2 Page Ref: Sec. 9.1-9.2
6) A heavy boy and a light girl are balanced on a massless seesaw. If they both move forward so
that they are one-half their original distance from the pivot point, what will happen to the
seesaw?
A) The side the boy is sitting on will tilt downward.
B) The side the girl is sitting on will tilt downward.
C) Nothing, the seesaw will still be balanced.
D) It is impossible to say without knowing the masses and the distances.
Answer: C
Diff: 2 Page Ref: Sec. 9.1-9.2
7) Muscles that tend to bring two limbs closer together are called
A) tendons.
B) flexors.
C) extensors.
D) insertions.
Answer: B
Diff: 1 Page Ref: Sec. 9.3
8) Muscles that act to extend a limb outward are called
A) tendons.
B) flexors.
C) extensors.
D) insertions.
Answer: C
Diff: 1 Page Ref: Sec. 9.3
9) A sphere hanging freely from a cord is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
Answer: A
Diff: 1 Page Ref: Sec. 9.4
169
, Chapter 9: Static Equilibrium; Elasticity and Fracture
10) A cone balanced on its small end is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
Answer: B
Diff: 1 Page Ref: Sec. 9.4
11) A cube resting on a horizontal tabletop is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
Answer: C
Diff: 1 Page Ref: Sec. 9.4
12) Consider two identical bricks, each of dimensions 20.0 cm ˛ 10.0 cm ˛ 6.0 cm. One is stacked
on the other, and the combination is then placed so that they project out over the edge of a
table. What is the maximum distance that the end of the top brick can extend beyond the table
edge without toppling?
A) 7.5 cm
B) 10 cm
C) 12.5 cm
D) 15 cm
Answer: D
Diff: 2 Page Ref: Sec. 9.4
13) A 36-kg round table is supported by three legs placed equal distances apart on the edge. What
minimum mass, placed in the middle between two supports on the table's edge, will cause the
table to overturn?
A) 12 kg
B) 24 kg
C) 36 kg
D) 48 kg
Answer: C
Diff: 3 Page Ref: Sec. 9.4
170
47) A proton of mass 1.67 ˛ 10-27 kg rotates with an angular speed of 2 ˛ 106 rad/s in a circle of
radius 0.80 m in a cyclotron. What is the orbital angular momentum of the proton?
A) 1.28 ˛ 10-21 kgœm2/s
B) 1.76 ˛ 10-21 kgœm2/s
C) 2.14 ˛ 10-21 kgœm2/s
D) 3.20 ˛ 10-21 kgœm2/s
Answer: C
Diff: 2 Page Ref: Sec. 8.8
48) An ice skater has a moment of inertia of 5.0 kgœm2 when her arms are outstretched. At this
time she is spinning at 3.0 revolutions per second (rps). If she pulls in her arms and decreases
her moment of inertia to 2.0 kgœm2, how fast will she be spinning?
A) 2.0 rps
B) 3.3 rps
C) 7.5 rps
D) 10 rps
Answer: C
Diff: 1 Page Ref: Sec. 8.8
49) A figure skater rotating at 5.00 rad/s with arms extended has a moment of inertia of
2.25 kgœm2. If the arms are pulled in so the moment of inertia decreases to 1.80 kgœm2, what is
the final angular speed?
A) 2.25 rad/s
B) 4.60 rad/s
C) 6.25 rad/s
D) 0.81 rad/s
Answer: C
Diff: 2 Page Ref: Sec. 8.8
167
,Chapter 9 Static Equilibrium; Elasticity and Fracture
Conceptual Questions
1) What condition or conditions are necessary for rotational equilibrium?
A) SFx = 0
B) SFx = 0, ST = 0
C) ST = 0
D) SFx = 0, SFy = 0
Answer: C
Diff: 1 Page Ref: Sec. 9.1-9.2
2) What condition or conditions are necessary for static equilibrium?
A) SFx = 0
B) SFx = 0, SFy = 0, ST = 0
C) ST = 0
D) SFx = 0, SFy = 0
Answer: B
Diff: 1 Page Ref: Sec. 9.1-9.2
3) A book weighs 6 N. When held at rest above your head the net force on the book is
A) 0 N.
B) 6 N.
C) 9.8 N.
D) -6 N.
Answer: A
Diff: 1 Page Ref: Sec. 9.1-9.2
4) A rocket moves through outer space with a constant velocity of 9.8 m/s. What net force acts
on it?
A) a force equal to its weight on Earth, mg
B) a force equal to the gravity acting on it
C) The net force is zero.
D) cannot be determined without more information
Answer: C
Diff: 1 Page Ref: Sec. 9.1-9.2
168
, Physics: Principles with Applications, Sixth Edition
5) A person weighing 800 N stands with one foot on each of two bathroom scales. Which
statement is definitely true?
A) Each scale will read 800 N.
B) Each scale will read 400 N.
C) If one scale reads 500 N, the other will read 300 N.
D) None of the above is definitely true.
Answer: C
Diff: 2 Page Ref: Sec. 9.1-9.2
6) A heavy boy and a light girl are balanced on a massless seesaw. If they both move forward so
that they are one-half their original distance from the pivot point, what will happen to the
seesaw?
A) The side the boy is sitting on will tilt downward.
B) The side the girl is sitting on will tilt downward.
C) Nothing, the seesaw will still be balanced.
D) It is impossible to say without knowing the masses and the distances.
Answer: C
Diff: 2 Page Ref: Sec. 9.1-9.2
7) Muscles that tend to bring two limbs closer together are called
A) tendons.
B) flexors.
C) extensors.
D) insertions.
Answer: B
Diff: 1 Page Ref: Sec. 9.3
8) Muscles that act to extend a limb outward are called
A) tendons.
B) flexors.
C) extensors.
D) insertions.
Answer: C
Diff: 1 Page Ref: Sec. 9.3
9) A sphere hanging freely from a cord is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
Answer: A
Diff: 1 Page Ref: Sec. 9.4
169
, Chapter 9: Static Equilibrium; Elasticity and Fracture
10) A cone balanced on its small end is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
Answer: B
Diff: 1 Page Ref: Sec. 9.4
11) A cube resting on a horizontal tabletop is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
Answer: C
Diff: 1 Page Ref: Sec. 9.4
12) Consider two identical bricks, each of dimensions 20.0 cm ˛ 10.0 cm ˛ 6.0 cm. One is stacked
on the other, and the combination is then placed so that they project out over the edge of a
table. What is the maximum distance that the end of the top brick can extend beyond the table
edge without toppling?
A) 7.5 cm
B) 10 cm
C) 12.5 cm
D) 15 cm
Answer: D
Diff: 2 Page Ref: Sec. 9.4
13) A 36-kg round table is supported by three legs placed equal distances apart on the edge. What
minimum mass, placed in the middle between two supports on the table's edge, will cause the
table to overturn?
A) 12 kg
B) 24 kg
C) 36 kg
D) 48 kg
Answer: C
Diff: 3 Page Ref: Sec. 9.4
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