Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. … IN.pdf · The drawing below represents a section of the Slinky at one instant in time. The direction the wave is

Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Cutnell/Johnson

Physics

Classroom Response System Questions

Chapter 16 Waves and Sound

Interactive Lecture Questions


16.1.1. A transverse wave is traveling along a Slinky. The drawing below represents a section of the

Slinky at one instant in time. The direction the wave is traveling is from left to right. Two

segments are labeled on the Slinky. At the instant shown, which of the following statements

correctly describes the motion of the particles that compose the Slinky in segments A and B?

a) In segment A the particles are moving downward and in segment B the particles are moving upward.

b) In segment A the particles are moving upward and in segment B the particles are moving upward.

c) In segment A the particles are moving downward and in segment B the particles are moving

downward.

d) In segment A the particles are moving upward and in segment B the particles are moving downward.

e) In segment A the particles are moving toward the left and in segment B the particles are moving

toward the right.


16.1.2. Mike is holding one end of a Slinky. His hand moves up and

down and causes a transverse wave to travel along the Slinky

away from him. Is the motion of Mike’s hand a wave?

a) Yes, the motion of Mike’s hand is a wave because it moves up and

down in periodic motion.

b) Yes, the motion of Mike’s hand is a wave because Mike is

transferring energy to the Slinky.

c) No, the motion of Mike’s hand is not a wave because there is no

traveling disturbance.

d) No, the motion of Mike’s hand is not a wave because there is no

energy traveling along the Slinky.


16.2.1. Jimmy and Jenny are floating on a quiet river using giant

doughnut-shaped tubes. At one point, they are 5.0 m apart when a

speed boat passes. After the boat passes, they begin bobbing up and

down at a frequency of 0.25 Hz. Just as Jenny reaches her highest

level, Jimmy is at his lowest level. Jenny and Jimmy are always less

than one wavelength apart. What is the speed of these waves?

a) 1.3 m/s

b) 2.5 m/s

c) 3.8 m/s

d) 5.0 m/s

e) 7.5 m/s


16.2.2. The drawing shows the vertical position of points along a

string versus distance as a wave travels along the string. Six points

on the wave are labeled A, B, C, D, E, and F. Between which two

points is the length of the segment equal to one wavelength?

a) A to E

b) B to D

c) A to C

d) A to F

e) C to F


16.2.3. A longitudinal wave with an amplitude of 0.02 m moves

horizontally along a Slinky with a speed of 2 m/s. Which one of the

following statements concerning this wave is true?

a) Each particle in the Slinky moves a distance of 2 m each second.

b) Each particle in the Slinky moves a horizontal distance of 0.04 m during

each period of the wave.

c) Each particle in the Slinky moves a horizontal distance of 0.08 m during


d) Each particle in the Slinky moves a vertical distance of 0.04 m during


e) Each particle in the Slinky has a wavelength of 0.04 m.


16.2.4. A sound wave is being emitted from a speaker with a

frequency f and an amplitude A. The sound waves travel at a

constant speed of 343 m/s in air. Which one of the following

actions would reduce the wavelength of the sound waves to one

half of their initial value?

a) increase the frequency to 2f

b) increase the amplitude to 2A

c) decrease the frequency to f /4

d) decrease the frequency to f /2

e) decrease the amplitude to A /2


16.3.1. The tension of a guitar string in increased by a factor of 4. How

does the speed of a wave on the string increase, if at all?

a) The speed of a wave is reduced to one-fourth the value it had before the

increase in tension.

b) The speed of a wave is reduced to one-half the value it had before the


c) The speed of a wave remains the same as before the increase in tension.

d) The speed of a wave is increased to two times the value it had before the


e) The speed of a wave is increased to four times the value it had before the



16.3.2. Two identical strings each have one end attached to a wall. The other ends are each attached to a

separate spool that allows the tension of each string to be changed independently. Consider each of

the waves shown. Which one of the following statements is true if the frequency and amplitude of

the waves is the same?

a) The tension in the string on which wave A is traveling is four times that in the string on which wave D

is traveling.

b) The tension in the string on which wave B is traveling is four times that in the string on which wave D

is traveling.

c) The tension in the string on which wave B is traveling is four times that in the string on which wave A

is traveling.

d) The tension in the string on which wave D is traveling is four times that in the string on which wave A

is traveling.

e) The tension in the string on which wave C is traveling is four times that in the string on which wave B

is traveling.


16.3.3. A climbing rope is hanging from the ceiling in a gymnasium.

A student grabs the end of the rope and begins moving it back

and forth with a constant amplitude and frequency. A transverse

wave moves up the rope. Which of the following statements

describing the speed of the wave is true?

a) The speed of the wave decreases as it moves upward.

b) The speed of the wave increases as it moves upward.

c) The speed of the wave is constant as it moves upward.

d) The speed of the wave does not depend on the mass of the rope.

e) The speed of the wave depends on its amplitude.


16.3.4. When a wire is stretched by a force F, the speed of a

traveling wave is v. What is the speed of the wave on the

wire when the force is doubled to 3F?

a) v

b) 3v

c) 9v

d)

e)

3v

3

v


16.4.1. A radio station broadcasts its radio signal at a frequency of

101.5 MHz. The signals travel radially outward from a tower at

the speed of light. Which one of the following equations

represents this wave if t is expressed in seconds and x is expressed

in meters? (The wave amplitude is A)

a) y = A sin[(6.377 108)t (2.123)x]

b) y = A sin[(637.7)t (2.961)x]

c) y = A sin[(6.283 106)t (2.961 103)x]

d) y = A sin[(101.5 106)t (2.961)x]

e) y = A sin[(101.5 106)t (2.123)x]


16.4.2. The equation for a certain wave is y = 4.0 sin [2(2.5t + 0.14x)]

where y and x are measured in meters and t is measured in seconds.

What is the magnitude and direction of the velocity of this wave?

a) 1.8 m/s in the +x direction

b) 1.8 m/s in the x direction

c) 18 m/s in the x direction

d) 7.2 m/s in the +x direction

e) 0.35 m/s in the x direction


16.4.3. Which one of the following statements correctly describes the wave given

as this equation: , where distances are measured in cm and

time is measured in ms?

a) The wave is traveling in the +x direction with an amplitude of 3 cm and a

wavelength of /2 cm.

b) The wave is traveling in the +x direction with an amplitude of 4 cm and a

wavelength of cm.

c) The wave is traveling in the +x direction with an amplitude of 3 cm and a

wavelength of cm.

d) The wave is traveling in the +x direction with an amplitude of 2 cm and a

wavelength of cm.

e) The wave is traveling in the +x direction with an amplitude of 6 cm and a

wavelength of /2 cm.

3 sin ( 4 2 )y x t


16.4.4. Which one of the following correctly describes a wave described by y =

2.0 sin(3.0x 2.0t) where y and x are measured in meters and t is measured

in seconds?

a) The wave is traveling in the +x direction with a frequency 6 Hz and a

wavelength 3 m.

b) The wave is traveling in the +x direction with a frequency 1/ Hz and a

wavelength 2/3 m.

c) The wave is traveling in the +x direction with a frequency Hz and a

wavelength 3/2 m.

d) The wave is traveling in the x direction with a frequency 4 Hz and a

wavelength m.

e) The wave is traveling in the -x direction with a frequency 1/ Hz and a

wavelength 2/3 m.


16.5.1. A particle of dust is floating in the air approximately one half meter in front of a

speaker. The speaker is then turned on produces a constant pure tone whose

frequency is shown. The sound waves produced by the speaker travel horizontally.

Which one of the following statements correctly describes the subsequent motion

of the dust particle, if any?

a) The particle of dust will oscillate left and right with a frequency of 226 Hz.

b) The particle of dust will oscillate up and down with a frequency of 226 Hz.

c) The particle of dust will be accelerated toward the right and continue moving in that

direction.

d) The particle of dust will move toward the right at constant velocity.

e) The dust particle will remain motionless as it cannot be affected by sound waves.


16.5.2. While constructing a rail line in the 1800s, spikes were driven

to attach the rails to cross ties with a sledge hammer. Consider the

sound that is generated by the vibrating spike each time the

hammer hits the spike. How does the frequency of the sound

change, if at all, as the spike is driven into the tie?

a) The frequency of the sound does not change as the spike is driven.

b) The frequency of the sound decreases as the spike is driven.

c) The frequency of the sound increases as the spike is driven.


16.6.1. In a classroom demonstration, a physics professor breathes in a small amount of

helium and begins to talk. The result is that the professor’s normally low, baritone

voice sounds quite high pitched. Which one of the following statements best

describes this phenomena?

a) The presence of helium changes the speed of sound in the air in the room, causing

all sounds to have higher frequencies.

b) The professor played a trick on the class by tightening his vocal cords to produces

higher frequencies in his throat and mouth than normal. The helium was only a

distraction and had nothing to do with it.

c) The helium significantly shortens the vocal chords causing the wavelength of the

sounds generated to decrease and thus the frequencies increase.

d) The wavelength of the sound generated in the professor’s throat and mouth is only

changed slightly, but since the speed of sound in helium is approximately 2.5 times

larger than in air, therefore the frequencies generated are about 2.5 times higher.


16.6.2. The graph shows measured data for the speed of sound in water and the density of the water

versus temperature. From the graph and your knowledge of the speed of sound in liquids, what can

we infer about the bulk modulus of water in the temperature range from 0 to 100 C?

a) The bulk modulus of water

increases linearly with

temperature.

b) The bulk modulus of water

decreases non-linearly with

temperature.

c) The bulk modulus of water

is constant with increasing

temperature.

d) The bulk modulus of water

increases with increasing

temperature.

e) The bulk modulus of water

increases with increasing temperature

until it peaks around 60 C after which it slowly decreases.


16.6.3. Ethanol has a density of 659 kg/m3. If the speed of sound

in ethanol is 1162 m/s, what is its adiabatic bulk modulus?

a) 1.74 108 N/m2

b) 2.23 108 N/m2

c) 7.72 108 N/m2

d) 8.90 108 N/m2

e) 6.18 109 N/m2


16.7.1. Natalie is a distance d in front of a speaker emitting sound

waves. She then moves to a position that is a distance 2d in front

of the speaker. By what percentage does the sound intensity

decrease for Natalie between the two positions?

a) 10 %

b) 25 %

c) 50 %

d) 75%

e) The sound intensity remains constant because it is not dependent

on the distance.


16.7.2. A bell is ringing inside of a sealed glass jar that is

connected to a vacuum pump. Initially, the jar is filled with

air at atmospheric pressure. What does one hear as the air is

slowly removed from the jar by the pump?

a) The sound intensity gradually increases.

b) The sound intensity gradually decreases.

c) The sound intensity of the bell does not change.

d) The frequency of the sound gradually increases.

e) The frequency of the sound gradually decreases.


16.8.1. A sound level meter is used measure the sound intensity level. A sound

level meter is placed an equal distance in front of two speakers, one to the

left and one to the right. A signal of constant frequency may be sent to

each of the speakers independently or at the same time. When either the

left speaker is turned on or the right speaker is turned on, the sound level

meter reads 90.0 dB. What will the sound level meter read when both

speakers are turned on at the same time?

a) 90.0 dB

b) 93.0 dB

c) 96.0 dB

d) 100.0 dB

e) 180.0 dB


16.8.2. A sound level meter is used measure the sound intensity level. A sound

level meter is placed an equal distance in front of two speakers, one to the

left and one to the right. A signal of constant frequency, but differing

amplitude, is sent to each speaker independently. When the left speaker is

turned on the sound level meter reads 85 dB. When the right speaker is

turned on the sound level meter reads 65 dB. What will the sound level

meter read when both speakers are turned on at the same time?

a) about 85 dB

b) about 65 dB

c) about 150 dB

d) about 75 dB

e) about 113 dB


16.8.3. Software is used to amplify a digital sound file on a computer

by 20 dB. By what factor has the intensity of the sound been

increased as compared to the original sound file?

a) 2

b) 5

c) 10

d) 20

e) 100


16.9.2. A child is swinging back and forth with a constant period and amplitude.

Somewhere in front of the child, a stationary horn is emitting a constant tone of

frequency fS. Five points are labeled in the drawing to indicate positions along

the arc as the child swings. At which position(s) will the child hear the lowest

frequency for the sound from the whistle?

a) at B when moving

toward A

b) at B when moving

toward C

c) at C when moving

toward B

d) at C when moving toward D

e) at both A and D


16.9.3. Hydrogen atoms in a distant galaxy are observed to emit light that

is shifted to lower frequencies with respect to hydrogen atoms here

on Earth. Astronomers use this information to determine the relative

velocity of the galaxy with respect to the Earth by observing how

light emitted by atoms is Doppler shifted. For the hydrogen atoms

mentioned, how are the wavelengths of light affected by the relative

motion, if at all?

a) The wavelengths would be unchanged, only the frequencies are

shifted.

b) The wavelengths of light would be longer than those observed on

Earth.

c) The wavelengths of light would be shorter than those observed on

Earth.

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Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. … IN.pdf · The drawing below represents a section of the Slinky at one instant in time. The direction the wave is