Cutnell/Johnson
Physics 7th edition
Classroom Response System Questions
Chapter 8 Rotational Kinematics
Interactive Lecture Questions
8.1.1. Over the course of a day (twenty-four hours), what is the
angular displacement of the second hand of a wrist watch in
radians?
a) 1440 rad
b) 2880 rad
c) 4520 rad
d) 9050 rad
e) 543 000 rad
8.1.1. Over the course of a day (twenty-four hours), what is the
angular displacement of the second hand of a wrist watch in
radians?
a) 1440 rad
b) 2880 rad
c) 4520 rad
d) 9050 rad
e) 543 000 rad
8.2.1. The planet Mercury takes only 88 Earth days to orbit the Sun.
The orbit is nearly circular, so for this exercise, assume that it is.
What is the angular velocity, in radians per second, of Mercury in
its orbit around the Sun?
a) 8.3 × 10-7 rad/s
b) 2.0 × 10-5 rad/s
c) 7.3 × 10-4 rad/s
d) 7.1 × 10-2 rad/s
e) This cannot be determined without knowing the radius of the orbit.
8.2.1. The planet Mercury takes only 88 Earth days to orbit the Sun.
The orbit is nearly circular, so for this exercise, assume that it is.
What is the angular velocity, in radians per second, of Mercury in
its orbit around the Sun?
a) 8.3 × 10-7 rad/s
b) 2.0 × 10-5 rad/s
c) 7.3 × 10-4 rad/s
d) 7.1 × 10-2 rad/s
e) This cannot be determined without knowing the radius of the orbit.
8.2.2. Complete the following statement: For a wheel that turns with
constant angular speed,
a) each point on its rim moves with constant acceleration.
b) the wheel turns through “equal angles in equal times.”
c) each point on the rim moves at a constant velocity.
d) the angular displacement of a point on the rim is constant.
e) all points on the wheel are moving at a constant velocity.
8.2.2. Complete the following statement: For a wheel that turns with
constant angular speed,
a) each point on its rim moves with constant acceleration.
b) the wheel turns through “equal angles in equal times.”
c) each point on the rim moves at a constant velocity.
d) the angular displacement of a point on the rim is constant.
e) all points on the wheel are moving at a constant velocity.
8.3.1. The propeller of an airplane is at rest when the pilot starts the
engine; and its angular acceleration is a constant value. Two
seconds later, the propeller is rotating at 10 rad/s. Through how
many revolutions has the propeller rotated through during the first
two seconds?
a) 300
b) 50
c) 20
d) 10
e) 5
8.3.1. The propeller of an airplane is at rest when the pilot starts the
engine; and its angular acceleration is a constant value. Two
seconds later, the propeller is rotating at 10 rad/s. Through how
many revolutions has the propeller rotated through during the first
two seconds?
a) 300
b) 50
c) 20
d) 10
e) 5
8.3.2. A ball is spinning about an axis that passes through its center
with a constant angular acceleration of  rad/s2. During a time
interval from t1 to t2, the angular displacement of the ball is 
radians. At time t2, the angular velocity of the ball is 2 rad/s.
What is the ball’s angular velocity at time t1?
a) 6.28 rad/s
b) 3.14 rad/s
c) 2.22 rad/s
d) 1.00 rad/s
e) zero rad/s
8.3.2. A ball is spinning about an axis that passes through its center
with a constant angular acceleration of  rad/s2. During a time
interval from t1 to t2, the angular displacement of the ball is 
radians. At time t2, the angular velocity of the ball is 2 rad/s.
What is the ball’s angular velocity at time t1?
a) 6.28 rad/s
b) 3.14 rad/s
c) 2.22 rad/s
d) 1.00 rad/s
e) zero rad/s
8.4.1. The Earth, which has an equatorial radius of 6380 km, makes
one revolution on its axis every 23.93 hours. What is the
tangential speed of Nairobi, Kenya, a city near the equator?
a) 37.0 m/s
b) 74.0 m/s
c) 148 m/s
d) 232 m/s
e) 465 m/s
8.4.1. The Earth, which has an equatorial radius of 6380 km, makes
one revolution on its axis every 23.93 hours. What is the
tangential speed of Nairobi, Kenya, a city near the equator?
a) 37.0 m/s
b) 74.0 m/s
c) 148 m/s
d) 232 m/s
e) 465 m/s
8.4.2. The original Ferris wheel had a radius of 38 m and completed a full
revolution (2p radians) every two minutes when operating at its
maximum speed. If the wheel were uniformly slowed from its
maximum speed to a stop in 35 seconds, what would be the
magnitude of the instantaneous tangential speed at the outer rim of
the wheel 15 seconds after it begins its deceleration?
a) 0.295 m/s
b) 1.12 m/s
c) 1.50 m/s
d) 1.77 m/s
e) 2.03 m/s
8.4.2. The original Ferris wheel had a radius of 38 m and completed a full
revolution (2p radians) every two minutes when operating at its
maximum speed. If the wheel were uniformly slowed from its
maximum speed to a stop in 35 seconds, what would be the
magnitude of the instantaneous tangential speed at the outer rim of
the wheel 15 seconds after it begins its deceleration?
a) 0.295 m/s
b) 1.12 m/s
c) 1.50 m/s
d) 1.77 m/s
e) 2.03 m/s
8.4.3. A long, thin rod of length 4L rotates counterclockwise with
constant angular acceleration around an axis that is perpendicular to
the rod and passes through a pivot point that is a length L from one
end as shown. What is the ratio of the tangential acceleration at a
point on the end closest to the pivot point to that at a point on the end
farthest from the pivot point?
a) 4
b) 3
c) 1/2
d) 1/3
e) 1/4
8.4.3. A long, thin rod of length 4L rotates counterclockwise with
constant angular acceleration around an axis that is perpendicular to
the rod and passes through a pivot point that is a length L from one
end as shown. What is the ratio of the tangential acceleration at a
point on the end closest to the pivot point to that at a point on the end
farthest from the pivot point?
a) 4
b) 3
c) 1/2
d) 1/3
e) 1/4
8.4.4. A long, thin rod of length 4L rotates counterclockwise with
constant angular acceleration around an axis that is perpendicular to
the rod and passes through a pivot point that is a length L from one
end as shown. What is the ratio of the tangential speed (at any
instant) at a point on the end closest to the pivot point to that at a
point on the end farthest from the pivot point?
a) 1/4
b) 1/3
c) 1/2
d) 3
e) 4
8.4.4. A long, thin rod of length 4L rotates counterclockwise with
constant angular acceleration around an axis that is perpendicular to
the rod and passes through a pivot point that is a length L from one
end as shown. What is the ratio of the tangential speed (at any
instant) at a point on the end closest to the pivot point to that at a
point on the end farthest from the pivot point?
a) 1/4
b) 1/3
c) 1/2
d) 3
e) 4
8.5.1. An airplane starts from rest at the end of a runway and begins
accelerating. The tires of the plane are rotating with an angular velocity
that is uniformly increasing with time. On one of the tires, Point A is
located on the part of the tire in contact with the runway surface and
point B is located halfway between Point A and the axis of rotation.
Which one of the following statements is true concerning this situation?
a) Both points have the same tangential acceleration.
b) Both points have the same centripetal acceleration.
c) Both points have the same instantaneous angular velocity.
d) The angular velocity at point A is greater than that of point B.
e) Each second, point A turns through a greater angle than point B.
8.5.1. An airplane starts from rest at the end of a runway and begins
accelerating. The tires of the plane are rotating with an angular velocity
that is uniformly increasing with time. On one of the tires, Point A is
located on the part of the tire in contact with the runway surface and
point B is located halfway between Point A and the axis of rotation.
Which one of the following statements is true concerning this situation?
a) Both points have the same tangential acceleration.
b) Both points have the same centripetal acceleration.
c) Both points have the same instantaneous angular velocity.
d) The angular velocity at point A is greater than that of point B.
e) Each second, point A turns through a greater angle than point B.
8.5.2. A wheel starts from rest and rotates with a constant angular
acceleration. What is the ratio of the instantaneous tangential
acceleration at point A located a distance 2r to that at point B
located at r, where the radius of the wheel is R = 2r?
a) 0.25
b) 0.50
c) 1.0
d) 2.0
e) 4.0
8.5.2. A wheel starts from rest and rotates with a constant angular
acceleration. What is the ratio of the instantaneous tangential
acceleration at point A located a distance 2r to that at point B
located at r, where the radius of the wheel is R = 2r?
a) 0.25
b) 0.50
c) 1.0
d) 2.0
e) 4.0
8.6.1. The wheels of a bicycle have a radius of r meters. The bicycle is traveling
along a level road at a constant speed v m/s. Which one of the following
expressions may be used to determine the angular speed, in rev/min, of the
wheels?
a)
b)
v
r
v
30 r
30 v
r
30 v
d)
2 r
60 v
e)
r
c)
8.6.1. The wheels of a bicycle have a radius of r meters. The bicycle is traveling
along a level road at a constant speed v m/s. Which one of the following
expressions may be used to determine the angular speed, in rev/min, of the
wheels?
a)
b)
v
r
v
30 r
30 v
r
30 v
d)
2 r
60 v
e)
r
c)
8.6.2. Josh is painting yellow stripes on a road using a paint roller. To
roll the paint roller along the road, Josh applies a force of 15 N at an
angle of 45 with respect to the road. The mass of the roller is 2.5 kg;
and its radius is 4.0 cm. Ignoring the mass of the handle of the roller,
what is the magnitude of the tangential acceleration of the roller?
a) 4.2 m/s2
b) 6.0 m/s2
c) 15 m/s2
d) 110 m/s2
e) 150 m/s2
8.6.2. Josh is painting yellow stripes on a road using a paint roller. To
roll the paint roller along the road, Josh applies a force of 15 N at an
angle of 45 with respect to the road. The mass of the roller is 2.5 kg;
and its radius is 4.0 cm. Ignoring the mass of the handle of the roller,
what is the magnitude of the tangential acceleration of the roller?
a) 4.2 m/s2
b) 6.0 m/s2
c) 15 m/s2
d) 110 m/s2
e) 150 m/s2
8.7.1. A packaged roll of paper towels falls from a shelf in a grocery
store and rolls due south without slipping. What is the direction of
the paper towels’ angular velocity?
a) north
b) east
c) south
d) west
e) down
8.7.1. A packaged roll of paper towels falls from a shelf in a grocery
store and rolls due south without slipping. What is the direction of
the paper towels’ angular velocity?
a) north
b) east
c) south
d) west
e) down
8.7.2. A packaged roll of paper towels falls from a shelf in a grocery
store and rolls due south without slipping. As its linear speed
slows, what are the directions of the paper towels’ angular velocity
and angular acceleration?
a) east, east
b) west, east
c) south, north
d) east, west
e) west, west
8.7.2. A packaged roll of paper towels falls from a shelf in a grocery
store and rolls due south without slipping. As its linear speed
slows, what are the directions of the paper towels’ angular velocity
and angular acceleration?
a) east, east
b) west, east
c) south, north
d) east, west
e) west, west
8.7.3. A top is spinning counterclockwise and moving toward the right
with a linear velocity as shown in the drawing. If the angular
speed is decreasing as time passes, what is the direction of the
angular velocity of the top?
a) upward
b) downward
c) left
d) right
8.7.3. A top is spinning counterclockwise and moving toward the right
with a linear velocity as shown in the drawing. If the angular
speed is decreasing as time passes, what is the direction of the
angular velocity of the top?
a) upward
b) downward
c) left
d) right
8.7.4. A truck and trailer have 18 wheels. If the direction of the
angular velocity vectors of the 18 wheels point 30 north of east, in
what direction is the truck traveling?
a) 30° east of south
b) 30° west of north
c) 30° north of east
d) 30° south of west
e) 30° south of east
8.7.4. A truck and trailer have 18 wheels. If the direction of the
angular velocity vectors of the 18 wheels point 30 north of east, in
what direction is the truck traveling?
a) 30° east of south
b) 30° west of north
c) 30° north of east
d) 30° south of west
e) 30° south of east
8.7.5. A girl is sitting on the edge of a merry-go-round at a playground
as shown. Looking down from above, the merry-go-round is
rotating clockwise. What is the direction of the girl’s angular
velocity?
a) upward
b) downward
c) left
d) right
e) There is no direction since it is the merry go round that has the
angular velocity.
8.7.5. A girl is sitting on the edge of a merry-go-round at a playground
as shown. Looking down from above, the merry-go-round is
rotating clockwise. What is the direction of the girl’s angular
velocity?
a) upward
b) downward
c) left
d) right
e) There is no direction since it is the merry go round that has the
angular velocity.