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Chapter 4 QuickCheck Questions
physics
FOR SCIENTISTS AND ENGINEERS
a strategic approach
THIRD EDITION
randall d. knight
© 2013 Pearson Education, Inc.
QuickCheck 4.2
A car is traveling around a curve
at a steady 45 mph. Is the car
accelerating?
A. Yes
B. No
© 2013 Pearson Education, Inc.
Slide 4-27
QuickCheck 4.2
A car is traveling around a curve
at a steady 45 mph. Is the car
accelerating?
A. Yes
B. No
© 2013 Pearson Education, Inc.
Slide 4-28
QuickCheck 4.3
A car is traveling around a
curve at a steady 45 mph.
Which vector shows the
direction of the car’s
acceleration?
E. The acceleration is zero.
© 2013 Pearson Education, Inc.
Slide 4-29
QuickCheck 4.3
A car is traveling around a
curve at a steady 45 mph.
Which vector shows the
direction of the car’s
acceleration?
E. The acceleration is zero.
© 2013 Pearson Education, Inc.
Slide 4-30
QuickCheck 4.4
A car is slowing down as it drives over a circular hill.
Which of these is the acceleration vector at the highest
point?
© 2013 Pearson Education, Inc.
Slide 4-34
QuickCheck 4.4
A car is slowing down as it drives over a circular hill.
Which of these is the acceleration vector at the highest
point?
Acceleration of
changing speed
Acceleration of
changing direction
© 2013 Pearson Education, Inc.
Slide 4-35
QuickCheck 4.10
This is the angular velocity graph
of a wheel. How many
revolutions does the
wheel make in the
first 4 s?
A.
B.
C.
D.
E.
1
2
4
6
8
© 2013 Pearson Education, Inc.
Slide 4-85
QuickCheck 4.10
This is the angular velocity graph
of a wheel. How many
revolutions does the
wheel make in the
first 4 s?
A.
B.
C.
D.
E.
1
2
4
6
8
© 2013 Pearson Education, Inc.
 = area under the angular velocity curve
Slide 4-86
QuickCheck 4.11
A ball rolls around a circular track with an
angular velocity of 4 rad/s. What is the
period of the motion?
A.
1
2
s
B. 1 s
C. 2 s
D.
E.
1
2
1
4
s
s
© 2013 Pearson Education, Inc.
Slide 4-88
QuickCheck 4.11
A ball rolls around a circular track with an
angular velocity of 4 rad/s. What is the
period of the motion?
A.
1
2
T
s
2

B. 1 s
C. 2 s
D.
E.
1
2
1
4
s
s
© 2013 Pearson Education, Inc.
Slide 4-89
QuickCheck 4.12
Rasheed and Sofia are riding a
merry-go-round that is spinning
steadily. Sofia is twice as far from
the axis as is Rasheed. Sofia’s
angular velocity is ______
that of Rasheed.
A.
half
B.
the same as
C.
twice
D.
four times
E.
We can’t say without knowing their radii.
© 2013 Pearson Education, Inc.
Slide 4-95
QuickCheck 4.12
Rasheed and Sofia are riding a
merry-go-round that is spinning
steadily. Sofia is twice as far from
the axis as is Rasheed. Sofia’s
angular velocity is ______
that of Rasheed.
A.
half
B.
the same as
C.
twice
D.
four times
E.
We can’t say without knowing their radii.
© 2013 Pearson Education, Inc.
Slide 4-96
QuickCheck 4.13
Rasheed and Sofia are riding a
merry-go-round that is spinning
steadily. Sofia is twice as far from
the axis as is Rasheed. Sofia’s
speed is ______ that of Rasheed.
A.
half
B.
the same as
C.
twice
D.
four times
E.
We can’t say without knowing their radii.
© 2013 Pearson Education, Inc.
Slide 4-97
QuickCheck 4.13
Rasheed and Sofia are riding a
merry-go-round that is spinning
steadily. Sofia is twice as far from
the axis as is Rasheed. Sofia’s
speed is ______ that of Rasheed.
A.
half
B.
the same as
C.
twice
D.
four times
E.
We can’t say without knowing their radii.
© 2013 Pearson Education, Inc.
v  r
Slide 4-98
QuickCheck 4.14
Rasheed and Sofia are riding a
merry-go-round that is spinning
steadily. Sofia is twice as far from
the axis as is Rasheed. Sofia’s
acceleration is ______ that
of Rasheed.
A.
half
B.
the same as
C.
twice
D.
four times
E.
We can’t say without knowing their radii.
© 2013 Pearson Education, Inc.
Slide 4-99
QuickCheck 4.14
Rasheed and Sofia are riding a
merry-go-round that is spinning
steadily. Sofia is twice as far from
the axis as is Rasheed. Sofia’s
acceleration is ______ that
of Rasheed.
A.
half
B.
the same as
C.
twice
D.
four times
E.
We can’t say without knowing their radii.
© 2013 Pearson Education, Inc.
v2
Centripetal acceleration a 
  2r
r
Slide 4-100
QuickCheck 4.15
The fan blade is slowing down.
What are the signs of ω and ?
A. ω is positive and  is positive.
B. ω is positive and  is negative.
C. ω is negative and  is positive.
D. ω is negative and  is negative.
E. ω is positive and  is zero.
© 2013 Pearson Education, Inc.
Slide 4-105
QuickCheck 4.15
The fan blade is slowing down.
What are the signs of ω and ?
A. ω is positive and  is positive.
B. ω is positive and  is negative.
C. ω is negative and  is positive.
D. ω is negative and  is negative.
E. ω is positive and  is zero.
“Slowing down” means that  and  have opposite signs, not
that  is negative
© 2013 Pearson Education, Inc.
Slide 4-106
QuickCheck 4.16
Starting from rest, a wheel with constant angular
acceleration turns through an angle of 25 rad in a time t.
Through what angle will it have turned after time 2t?
A. 25 rad
B. 50 rad
C. 75 rad
D. 100 rad
E. 200 rad
© 2013 Pearson Education, Inc.
Slide 4-108
QuickCheck 4.16
Starting from rest, a wheel with constant angular
acceleration turns through an angle of 25 rad in a time t.
Through what angle will it have turned after time 2t?
A. 25 rad
B. 50 rad
C. 75 rad
D. 100 rad
  (t)2
E. 200 rad
© 2013 Pearson Education, Inc.
Slide 4-109
QuickCheck 4.17
Starting from rest, a wheel with constant angular
acceleration spins up to 25 rpm in a time t. What will
its angular velocity be after time 2t?
A. 25 rpm
B. 50 rpm
C. 75 rpm
D. 100 rpm
E. 200 rpm
© 2013 Pearson Education, Inc.
Slide 4-110
QuickCheck 4.17
Starting from rest, a wheel with constant angular
acceleration spins up to 25 rpm in a time t. What will
its angular velocity be after time 2t?
A. 25 rpm
B. 50 rpm
  t
C. 75 rpm
D. 100 rpm
E. 200 rpm
© 2013 Pearson Education, Inc.
Slide 4-111
QuickCheck 8.2
A toy car moves around a circular track at constant
speed. It suddenly doubles its speed — a change
of a factor of 2. As a result, the centripetal
acceleration changes by a factor of
A. 1/4.
B. 1/2.
C. No change since the radius doesn’t change.
D. 2.
E. 4.
© 2013 Pearson Education, Inc.
Slide 8-38
QuickCheck 8.2
A toy car moves around a circular track at constant
speed. It suddenly doubles its speed—a change of
a factor of 2. As a result, the centripetal
acceleration changes by a factor of
A. 1/4.
B. 1/2.
C. No change since the radius doesn’t change.
D. 2.
E. 4.
© 2013 Pearson Education, Inc.
Slide 8-39
QuickCheck 8.3
An ice hockey puck is tied by a string
to
a stake in the ice. The puck is then
swung in a circle. What force or forces
does the puck feel?
A.
B.
C.
D.
E.
A new force: the centripetal force.
A new force: the centrifugal force.
One or more of our familiar forces pushing outward.
One or more of our familiar forces pulling inward.
I have no clue.
© 2013 Pearson Education, Inc.
Slide 8-44
QuickCheck 8.3
An ice hockey puck is tied by a string
to
a stake in the ice. The puck is then
swung in a circle. What force or forces
does the puck feel?
A.
B.
C.
D.
E.
A new force: the centripetal force.
A new force: the centrifugal force.
One or more of our familiar forces pushing outward.
One or more of our familiar forces pulling inward.
I have no clue.
The rules about what is or is not a force haven’t changed:
1. Force must be exerted at a point of contact (except for gravity).
2. Force must have an identifiable agent doing the pushing or pulling.
3. The net force must point in the direction of acceleration (Newton’s second
law).
© 2013 Pearson Education, Inc.
Slide 8-45
QuickCheck 8.4
An ice hockey puck is tied by a
string to a stake in the ice. The
puck is then swung in a circle.
What force is producing the
centripetal acceleration of the
puck?
A.
Gravity
B.
Air resistance
C.
Friction
D.
Normal force
E.
Tension in the string
© 2013 Pearson Education, Inc.
Slide 8-46
QuickCheck 8.4
An ice hockey puck is tied by a
string to a stake in the ice. The
puck is then swung in a circle.
What force is producing the
centripetal acceleration of the
puck?
A.
Gravity
B.
Air resistance
C.
Friction
D.
Normal force
E.
Tension in the string
© 2013 Pearson Education, Inc.
Slide 8-47
QuickCheck 8.5
A car turns a corner on a
banked road. Which of the
diagrams could be the car’s
free-body diagram?
© 2013 Pearson Education, Inc.
Slide 8-56
QuickCheck 8.5
A car turns a corner on a
banked road. Which of the
diagrams could be the car’s
free-body diagram?
© 2013 Pearson Education, Inc.
Slide 8-57
QuickCheck 8.6
A coin sits on a turntable as the
table steadily rotates ccw. The
free-body diagrams below show
the coin from behind, moving
away from you. Which is the
correct diagram?
© 2013 Pearson Education, Inc.
Slide 8-66
QuickCheck 8.6
A coin sits on a turntable as the
table steadily rotates ccw. The
free-body diagrams below show
the coin from behind, moving
away from you. Which is the
correct diagram?
© 2013 Pearson Education, Inc.
Slide 8-67
QuickCheck 8.7
A coin sits on a turntable as the
table steadily rotates ccw. What
force or forces act in the plane of
the turntable?
© 2013 Pearson Education, Inc.
Slide 8-68
QuickCheck 8.7
A coin sits on a turntable as the
table steadily rotates ccw. What
force or forces act in the plane of
the turntable?
© 2013 Pearson Education, Inc.
Slide 8-69
QuickCheck 8.8
Two coins are on a turntable
that steadily speeds up,
starting from rest, with a ccw
rotation. Which coin flies off
the turntable first?
A.
Coin 1 flies off first.
B.
Coin 2 flies off first.
C.
Both coins fly off at the same time.
D.
We can’t say without knowing their
masses.
© 2013 Pearson Education, Inc.
Slide 8-70
QuickCheck 8.8
Two coins are on a turntable
that steadily speeds up,
starting from rest, with a ccw
rotation. Which coin flies off
the turntable first?
A.
Coin 1 flies off first.
B.
Coin 2 flies off first.
C.
Both coins fly off at the same time.
D.
We can’t say without knowing their
masses.
© 2013 Pearson Education, Inc.
Slide 8-71
QuickCheck 8.9
A physics textbook swings back
and forth as a pendulum. Which
is the correct free-body diagram
when the book is at the bottom
and moving to the right?
© 2013 Pearson Education, Inc.
Slide 8-78
QuickCheck 8.9
A physics textbook swings back
and forth as a pendulum. Which
is the correct free-body diagram
when the book is at the bottom
and moving to the right?
© 2013 Pearson Education, Inc.
Centripetal acceleration
requires an upward
force.
Slide 8-79
QuickCheck 8.10
A car that’s out of gas coasts
over the top of a hill at a
steady 20 m/s. Assume air
resistance is negligible.
Which free-body diagram
describes the car at this
instant?
© 2013 Pearson Education, Inc.
Slide 8-80
QuickCheck 8.10
A car that’s out of gas coasts
over the top of a hill at a
steady 20 m/s. Assume air
resistance is negligible.
Which free-body diagram
describes the car at this
instant?
© 2013 Pearson Education, Inc.
Now the centripetal
acceleration points
down.
Slide 8-81
QuickCheck 8.11
A roller coaster car does a
loop-the-loop. Which of the
free-body diagrams shows the
forces on the car at the top of
the loop? Rolling friction can
be neglected.
© 2013 Pearson Education, Inc.
Slide 8-82
QuickCheck 8.11
A roller coaster car does a
loop-the-loop. Which of the
free-body diagrams shows the
forces on the car at the top of
the loop? Rolling friction can
be neglected.
© 2013 Pearson Education, Inc.
The track is above the car, so
the normal force of the track
pushes down.
Slide 8-83
QuickCheck 8.12
A ball rolls ccw around the
inside of a horizontal pipe. The
ball is fastest at the lowest
point, slowest at the highest
point. At the point shown, with
the ball moving down, what is
the direction of the net force on
the ball?
© 2013 Pearson Education, Inc.
Slide 8-90
QuickCheck 8.12
A ball rolls ccw around the
inside of a horizontal pipe. The
ball is fastest at the lowest
point, slowest at the highest
point. At the point shown, with
the ball moving down, what is
the direction of the net force on
the ball?
© 2013 Pearson Education, Inc.
Slide 8-91