COLLEGE PHYSICS FREEDMAN CHAPTER 28
COMPREHENSIVE STUDY QUESTIONS AND
ANSWERS
◉ What is the angular speed in rad/s of the second hand of a watch?
A) 1.7 × 10-3 rad/s
B) 0.10 rad/s
C) 0.02 rad/s
D) 6.28 rad/s
E) 60 rad/s.
Answer: B) 0.10 rad/s
◉ The Earth takes slightly less than one day to complete one
rotation about the axis passing through its poles. The actual time is
8.616 × 104 s. Given this information, what is the angular speed of
the Earth about its axis?
A) 7.292 × 10-5 rad/s
B) 2.321 × 10-6 rad/s
C) 9.951 × 10-5 rad/s
D) 6.334 × 10-4 rad/s
E) 1.990 × 10-7 rad/s.
Answer: A) 7.292 × 10-5 rad/s
,◉ A wheel with a 0.10-m radius is rotating at 35 rev/s. It then slows
uniformly to 15 rev/s over a 3.0-s interval. What is the angular
acceleration of a point on the wheel?
A) -2.0 rev/s2
B) 0.67 rev/s2
C) -6.7 rev/s2
D) 42 rev/s2
E) -17 rev/s2.
Answer: C) -6.7 rev/s2
◉ During the spin-dry cycle of a washing machine, the motor slows
from 90 rad/s to 30 rad/s while the turning the drum through an
angle of 180 radians. What is the magnitude of the angular
acceleration of the motor?
A) 64 rad/s2
B) 32 rad/s2
C) 10 rad/s2
D) 20 rad/s2
E) 1.0 rad/s2.
Answer: D) 20 rad/s2
,◉ A fan rotating with an initial angular velocity of 1000 rev/min is
switched off. In 2 seconds, the angular velocity decreases to 200
rev/min. Assuming the angular acceleration is constant, how many
revolutions does the blade undergo during this time?
A) 10
B) 20
C) 100
D) 125
E) 1200.
Answer: B) 20
◉ An airplane engine starts from rest; and 2 seconds later, it is
rotating with an angular speed of 420 rev/min. If the angular
acceleration is constant, how many revolutions does the propeller
undergo during this time?
A) 7
B) 14
C) 21
D) 49
E) 150.
Answer: A) 7
◉ During the time a compact disc (CD) accelerates from rest to a
constant rotational speed of 477 rev/min, it rotates through an
, angular displacement of 0.250 rev. What is the angular acceleration
of the CD?
A) 358 rad/s2
B) 126 rad/s2
C) 901 rad/s2
D) 866 rad/s2
E) 794 rad/s2.
Answer: E) 794 rad/s2
◉ A grindstone of radius 4.0 m is initially spinning with an angular
speed of 8.0 rad/s. The angular speed is then increased to 12 rad/s
over the next 4.0 seconds. Assume that the angular acceleration is
constant.
What is the average angular speed of the grindstone?
A) 0.5 rad/s
B) 2.0 rad/s
C) 4.0 rad/s
D) 8.0 rad/s
E) 10 rad/s.
Answer: E) 10 rad/s
◉ A grindstone of radius 4.0 m is initially spinning with an angular
speed of 8.0 rad/s. The angular speed is then increased to 12 rad/s
COMPREHENSIVE STUDY QUESTIONS AND
ANSWERS
◉ What is the angular speed in rad/s of the second hand of a watch?
A) 1.7 × 10-3 rad/s
B) 0.10 rad/s
C) 0.02 rad/s
D) 6.28 rad/s
E) 60 rad/s.
Answer: B) 0.10 rad/s
◉ The Earth takes slightly less than one day to complete one
rotation about the axis passing through its poles. The actual time is
8.616 × 104 s. Given this information, what is the angular speed of
the Earth about its axis?
A) 7.292 × 10-5 rad/s
B) 2.321 × 10-6 rad/s
C) 9.951 × 10-5 rad/s
D) 6.334 × 10-4 rad/s
E) 1.990 × 10-7 rad/s.
Answer: A) 7.292 × 10-5 rad/s
,◉ A wheel with a 0.10-m radius is rotating at 35 rev/s. It then slows
uniformly to 15 rev/s over a 3.0-s interval. What is the angular
acceleration of a point on the wheel?
A) -2.0 rev/s2
B) 0.67 rev/s2
C) -6.7 rev/s2
D) 42 rev/s2
E) -17 rev/s2.
Answer: C) -6.7 rev/s2
◉ During the spin-dry cycle of a washing machine, the motor slows
from 90 rad/s to 30 rad/s while the turning the drum through an
angle of 180 radians. What is the magnitude of the angular
acceleration of the motor?
A) 64 rad/s2
B) 32 rad/s2
C) 10 rad/s2
D) 20 rad/s2
E) 1.0 rad/s2.
Answer: D) 20 rad/s2
,◉ A fan rotating with an initial angular velocity of 1000 rev/min is
switched off. In 2 seconds, the angular velocity decreases to 200
rev/min. Assuming the angular acceleration is constant, how many
revolutions does the blade undergo during this time?
A) 10
B) 20
C) 100
D) 125
E) 1200.
Answer: B) 20
◉ An airplane engine starts from rest; and 2 seconds later, it is
rotating with an angular speed of 420 rev/min. If the angular
acceleration is constant, how many revolutions does the propeller
undergo during this time?
A) 7
B) 14
C) 21
D) 49
E) 150.
Answer: A) 7
◉ During the time a compact disc (CD) accelerates from rest to a
constant rotational speed of 477 rev/min, it rotates through an
, angular displacement of 0.250 rev. What is the angular acceleration
of the CD?
A) 358 rad/s2
B) 126 rad/s2
C) 901 rad/s2
D) 866 rad/s2
E) 794 rad/s2.
Answer: E) 794 rad/s2
◉ A grindstone of radius 4.0 m is initially spinning with an angular
speed of 8.0 rad/s. The angular speed is then increased to 12 rad/s
over the next 4.0 seconds. Assume that the angular acceleration is
constant.
What is the average angular speed of the grindstone?
A) 0.5 rad/s
B) 2.0 rad/s
C) 4.0 rad/s
D) 8.0 rad/s
E) 10 rad/s.
Answer: E) 10 rad/s
◉ A grindstone of radius 4.0 m is initially spinning with an angular
speed of 8.0 rad/s. The angular speed is then increased to 12 rad/s
