AP Physics 1 Review Chs 16&17 – Mechanical Waves
• Understand the difference between longitudinal and transverse waves and know examples of each
• Know how to determine/calculate speed of a wave, amplitude, wavelength, frequency, period, and
distance traveled (including distances involving echoes)
• Understand the factors that affect the speed of a wave in a given medium and what happens to speed,
wavelength, and frequency of a wave as it passes from one medium into a medium with different
properties (speed and wavelength change proportionally while frequency remains constant)
• Understand the basic structure of a sound wave (longitudinal wave); know that the speed of sound is
typically fastest in a solid and increases with increasing temperature in a gas
• Know that amplitude determines loudness and frequency determines pitch
• Know that intensity decreases by the inverse square law but volume does not (10X intensity is heard
as about twice as loud)
• Understand the Doppler effect and how changes in speed of source or observer affect  and f
• Understand shock waves and wave forms with moving versus stationary sources
• Understand constructive and destructive interference and be able to apply the superposition principle
• Understand reflection of a wave at a free or fixed boundary
• Understand standing waves, nodes, antinodes, and be able to determine wavelength for a given
standing wave pattern
• Harmonics for a string, open-pipe resonator, and closed-pipe resonator
• Beat frequency
Slide 15-1
Which of the following actions would make a pulse travel
faster down a stretched string?
A. Move your hand up and down more quickly as you
generate the pulse.
B. Move your hand up and down a larger distance as
you generate the pulse.
C. Use a heavier string of the same length, under the
same tension.
D. Use a lighter string of the same length, under the
same tension.
E. Use a longer string of the same thickness, density
and tension.
Which of the following actions would make a pulse travel
faster down a stretched string?
A. Move your hand up and down more quickly as you
generate the pulse.
B. Move your hand up and down a larger distance as
you generate the pulse.
C. Use a heavier string of the same length, under the
same tension.
D. Use a lighter string of the same length, under
the same tension.
E. Use a longer string of the same thickness, density
and tension.
What is the frequency of this
traveling wave?
A. 10 Hz
B. 5 Hz
C. 2 Hz
D. 0.2 Hz
E. 0.1 Hz
What is the frequency of this
traveling wave?
A. 10 Hz
B. 5 Hz
C. 2 Hz
D. 0.2 Hz
E. 0.1 Hz
Amy and Zack are both listening to the source of sound
waves that is moving to the right. Compare the
frequencies each hears.
A. fAmy < fZack
B. fAmy = fZack
C. fAmy > fZack
Amy and Zack are both listening to the source of sound
waves that is moving to the right. Compare the
frequencies each hears.
A. fAmy < fZack
B. fAmy = fZack
C. fAmy > fZack
Two pulses on a string approach each other at speeds
of 1 m/s. What is the shape of the string at t = 6 s?
Two pulses on a string approach each other at speeds
of 1 m/s. What is the shape of the string at t = 6 s?
You hear three beats per second when two sound tones
are generated. The frequency of one tone is known to
be 610 Hz. The frequency of the other is
A. 604 Hz.
B. 607 Hz.
C. 613 Hz.
D. 616 Hz.
E. Either b or c.
You hear 3 beats per s when two sound tones are
generated. The frequency of one tone is known to be
610 Hz. The frequency of the other is
A. 604 Hz.
B. 607 Hz.
C. 613 Hz.
D. 616 Hz.
E. Either b or c.
When a wave pulse on a string reflects from a fixed
boundary, how is the reflected pulse related to the
incident pulse?
A. Shape unchanged, amplitude unchanged
B. Shape inverted, amplitude unchanged
C. Shape unchanged, amplitude reduced
D. Shape inverted, amplitude reduced
E. Amplitude unchanged, speed reduced
When a wave pulse on a string reflects from a fixed
boundary, how is the reflected pulse related to the
incident pulse?
A. Shape unchanged, amplitude unchanged
B. Shape inverted, amplitude unchanged
C. Shape unchanged, amplitude reduced
D. Shape inverted, amplitude reduced
E. Amplitude unchanged, speed reduced
The frequency of the third harmonic of a string is
A. one-third the frequency of the fundamental.
B. equal to the frequency of the fundamental.
C. three times the frequency of the fundamental.
D. nine times the frequency of the fundamental.
The frequency of the third harmonic of a string is
A. one-third the frequency of the fundamental.
B. equal to the frequency of the fundamental.
C. three times the frequency of the fundamental.
D. nine times the frequency of the fundamental.
These two wave pulses travel
along the same stretched
string, one after the other.
Which is true?
A.
B.
C.
D.
vA > vB
vB > vA
vA = vB
Not enough information to tell
© 2015 Pearson Education, Inc.
Slide 15-16
These two wave pulses travel
along the same stretched
string, one after the other.
Which is true?
A.
B.
C.
D.
vA > vB
vB > vA
Wave speed depends on the properties of the medium,
vA = vB not on the amplitude of the wave.
Not enough information to tell
© 2015 Pearson Education, Inc.
Slide 15-17
The period of this wave is
A.
B.
C.
D.
1s
2s
4s
Not enough information to tell
© 2015 Pearson Education, Inc.
Slide 15-18
The period of this wave is
A.
B.
C.
D.
1 s A sinusoidal wave moves
2 s forward one wavelength
4 s (2 m) in one period.
Not enough information to tell
© 2015 Pearson Education, Inc.
Slide 15-19
Which has a longer wavelength?
A. A 400-Hz sound wave in air
B. A 400-Hz sound wave in water
© 2015 Pearson Education, Inc.
Slide 15-20
Which has a longer wavelength?
A. A 400-Hz sound wave in air
B. A 400-Hz sound wave in water
© 2015 Pearson Education, Inc.
Slide 15-21
A wave bounces back and forth on a guitar string; this is
responsible for making the sound of the guitar. As the
temperature of the string rises, the tension decreases.
This ______ the speed of the wave on the string.
A. Increases
B. Does not change
C. Decreases
© 2015 Pearson Education, Inc.
Slide 15-22
A wave bounces back and forth on a guitar string; this is
responsible for making the sound of the guitar. As the
temperature of the string rises, the tension decreases.
This ______ the speed of the wave on the string.
A. Increases
B. Does not change
C. Decreases
© 2015 Pearson Education, Inc.
Slide 15-23
A speaker emits a 400-Hz tone. The air temperature
increases. This ______ the wavelength of the sound.
A. Increases
B. Does not change
C. Decreases
© 2015 Pearson Education, Inc.
Slide 15-24
A speaker emits a 400-Hz tone. The air temperature
increases. This ______ the wavelength of the sound.
A. Increases
B. Does not change
C. Decreases
© 2015 Pearson Education, Inc.
Slide 15-25
A wave on a string is traveling to the right. At this instant,
the motion of the piece of string marked with a dot is
A.
B.
C.
D.
E.
Up.
Down.
Right.
Left.
Zero, instantaneously at rest.
© 2015 Pearson Education, Inc.
Slide 15-26
A wave on a string is traveling to the right. At this instant,
the motion of the piece of string marked with a dot is
A.
B.
C.
D.
E.
Up.
Down.
Right.
Left.
Zero, instantaneously at rest.
© 2015 Pearson Education, Inc.
Slide 15-27
A siren emits a sound wave with
frequency f0. The graph shows the
frequency you hear as you stand
at rest at x = 0 on the x-axis. Which
is the correct description of the
siren’s motion?
A. It moves from left to right and passes you at t = 2 s.
B. It moves from right to left and passes you at t = 2 s.
C. It moves toward you for 2 s but doesn’t reach you, then reverses
direction at t = 2 s and moves away.
D. It moves away from you for 2 s, then reverses direction at t = 2 s
and moves toward you but doesn’t reach you.
© 2015 Pearson Education, Inc.
Slide 15-28
A siren emits a sound wave with
frequency f0. The graph shows the
frequency you hear as you stand
at rest at x = 0 on the x-axis. Which
is the correct description of the
siren’s motion?
Doppler shift to lower
frequency means it’s
moving away.
A. It moves from left to right and passes you at t = 2 s.
B. It moves from right to left and passes you at t = 2 s.
C. It moves toward you for 2 s but doesn’t reach you, then reverses
direction at t = 2 s and moves away.
D. It moves away from you for 2 s, then reverses direction at t = 2 s
and moves toward you but doesn’t reach you.
© 2015 Pearson Education, Inc.
Slide 15-29
Two wave pulses on a string
approach each other at
speeds of 1 m/s. How does
the string look at t = 3 s?
© 2015 Pearson Education, Inc.
Slide 15-30
Two wave pulses on a string
approach each other at
speeds of 1 m/s. How does
the string look at t = 3 s?
C.
© 2015 Pearson Education, Inc.
Slide 15-31
Two wave pulses on a string
approach each other at
speeds of 1 m/s. How does
the string look at t = 3 s?
© 2015 Pearson Education, Inc.
Slide 15-32
Two wave pulses on a string
approach each other at
speeds of 1 m/s. How does
the string look at t = 3 s?
B.
© 2015 Pearson Education, Inc.
Slide 15-33
What is the wavelength of this standing wave?
A.
B.
C.
D.
E.
0.25 m
0.5 m
1.0 m
2.0 m
Standing waves don’t have a wavelength.
© 2015 Pearson Education, Inc.
Slide 15-34
What is the wavelength of this standing wave?
A.
B.
C.
D.
E.
0.25 m
0.5 m
1.0 m
2.0 m
Standing waves don’t have a wavelength.
© 2015 Pearson Education, Inc.
Slide 15-35
Which of the following changes will increase the frequency
of the lowest-frequency standing sound wave on a stretched
string? Choose all that apply.
A.
B.
C.
D.
Replacing the string with a thicker string
Increasing the tension in the string
Plucking the string harder
Doubling the length of the string
© 2015 Pearson Education, Inc.
Slide 15-36
Which of the following changes will increase the frequency
of the lowest-frequency standing sound wave on a stretched
string? Choose all that apply.
A.
B.
C.
D.
Replacing the string with a thicker string
Increasing the tension in the string
Plucking the string harder
Doubling the length of the string
© 2015 Pearson Education, Inc.
Slide 15-37
An open-open tube of air has length
L. Which graph shows the standing
wave for the third harmonic in this
tube?
© 2015 Pearson Education, Inc.
Slide 15-38
An open-open tube of air has length
L. Which graph shows the standing
wave for the third harmonic in this
tube?
B.
© 2015 Pearson Education, Inc.
Slide 15-39
An open-closed tube of air of length L
has the closed end on the right. Which
graph shows the standing wave for
the third harmonic in this tube?
© 2015 Pearson Education, Inc.
Slide 15-40
An open-closed tube of air of length L
has the closed end on the right. Which
graph shows the standing wave for
the third harmonic in this tube?
D.
© 2015 Pearson Education, Inc.
Slide 15-41
The following tubes all support sound waves at their
fundamental frequency. Which tube has the lowest
fundamental frequency?
© 2015 Pearson Education, Inc.
Slide 15-42
The following tubes all support sound waves at their
fundamental frequency. Which tube has the lowest
fundamental frequency?
C.
© 2015 Pearson Education, Inc.
Slide 15-43
Which of the following changes will increase the frequency
of the lowest-frequency standing sound wave in an openopen tube? Choose all that apply.
A.
B.
C.
D.
Closing one end of the tube
Replacing the air in the tube with helium
Reducing the length of the tube
Increasing the temperature of the air in the tube
© 2015 Pearson Education, Inc.
Slide 15-44
Which of the following changes will increase the frequency
of the lowest-frequency standing sound wave in an openopen tube? Choose all that apply.
A.
B.
C.
D.
Closing one end of the tube
Replacing the air in the tube with helium
Reducing the length of the tube
Increasing the temperature of the air in the tube
© 2015 Pearson Education, Inc.
Slide 15-45
At room temperature, the fundamental frequency of an
open-open tube is 500 Hz. If taken outside on a cold winter
day, the fundamental frequency will be
A. Less than 500 Hz
B. 500 Hz
C. More than 500 Hz
© 2015 Pearson Education, Inc.
Slide 15-46
At room temperature, the fundamental frequency of an
open-open tube is 500 Hz. If taken outside on a cold winter
day, the fundamental frequency will be
A. Less than 500 Hz
B. 500 Hz
C. More than 500 Hz
© 2015 Pearson Education, Inc.
Slide 15-47
Two speakers emit sounds of nearly equal frequency, as
shown. At a point between the two speakers, the sound
varies from loud to soft. How much time elapses between
two successive loud moments?
A.
B.
C.
D.
0.5 s
1.0 s
2.0 s
4.0 s
© 2015 Pearson Education, Inc.
Slide 15-48
Two speakers emit sounds of nearly equal frequency, as
shown. At a point between the two speakers, the sound
varies from loud to soft. How much time elapses between
two successive loud moments?
A.
B.
C.
D.
0.5 s
1.0 s
2.0 s
4.0 s
© 2015 Pearson Education, Inc.
Slide 15-49