Question 1

Which one of the curves shown in the figure best represents the variation of wave speed v as a function of tension for transverse waves on a stretched string?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 2

A 1.1-kg uniform bar of metal is 0.40 m long and has a diameter of 2.0 cm. When someone bangs one end of this bar, a 1.5 MHz shock wave is travels along the length of the bar and reaches the other end in 0.12 ms. What is the wavelength of the shock wave in the metal?

Accepted Answer

A)  2.2 mm 
B)  2.6 mm 
C)  3.0 mm 
D)  3.4 mm 
E)  3.8 mm 
A)  2.2 mm 
B)  2.6 mm 
C)  3.0 mm 
D)  3.4 mm 
E)  3.8 mm

Question 3

The speed of sound in steel is 5000 m/s. What is the wavelength of a sound wave of frequency $660 \mathrm {~Hz}$ in steel?

Accepted Answer

A)  7.58 m 
B)  2.41 m 
C)  1.21 m 
D)  0.829 m 
E)  0.132 m 
A)  7.58 m 
B)  2.41 m 
C)  1.21 m 
D)  0.829 m 
E)  0.132 m

Question 4

You are driving along a highway at 25 m/s when you hear the siren of an emergency vehicle traveling at constant speed in the opposite direction on the other side of the highway. When the vehicle is approaching you, you hear the frequency of the siren as 2380 Hz, but when it is past you the frequency becomes 1680 Hz. What is the speed of the vehicle? The speed of sound in air is 343 m/s.

Accepted Answer

A)  35 m/s 
B)  32 m/s 
C)  30 m/s 
D)  41 m/s 
E)  50 m/s 
A)  35 m/s 
B)  32 m/s 
C)  30 m/s 
D)  41 m/s 
E)  50 m/s

Question 5

A certain siren radiates sound uniformly in all directions. At a distance of 17 m from the siren, the intensity level is 49 db. How many watts of power does this siren put out? The threshold of human hearing is 1.0 × 10-12 W/m2.

Accepted Answer

Question 6

Sonar is used to determine the speed of an object. A 40.0-kHz signal is sent out, and a 42.0-kHz signal is returned. If the speed of sound is 345 m/s, how fast is the object moving?

Accepted Answer

A)  6.9 m/s 
B)  8.4 m/s 
C)  331 m/s 
D)  347 m/s 
A)  6.9 m/s 
B)  8.4 m/s 
C)  331 m/s 
D)  347 m/s

Question 7

Transverse waves travel at $43.2 \mathrm {~m} / \mathrm { s }$ in a string that is subjected to a tension of $60.5 \mathrm {~N}$ If the string is $15.9 \mathrm {~m}$ long, what is its mass?

Accepted Answer

A)  0.515 kg 
B)  0.216 kg 
C)  0.366 kg 
D)  0.597 kg 
A)  0.515 kg 
B)  0.216 kg 
C)  0.366 kg 
D)  0.597 kg

Question 8

The average intensity of sunlight impinging on Earth is measured to be about 1.4 kW/m2. What is the power of sunlight emitted by the sun? (Earth-Sun distance = 1.5 × 108 km, Earth radius = 6.4 × 103 km)

Accepted Answer

A)  4.0 × 1026 W 
B)  3.2 × 1022 W 
C)  7.2 × 1014 W 
D)  7.6 × 108 W 
A)  4.0 × 1026 W 
B)  3.2 × 1022 W 
C)  7.2 × 1014 W 
D)  7.6 × 108 W

Question 9

An earthquake generates three kinds of waves: surface waves (L-waves), which are the slowest and weakest, shear (S) waves, which are transverse waves and carry most of the energy, and pressure (P) waves, which are longitudinal waves and are the fastest. The speed of P waves is approximately 7 km/s, and that of S waves is about 4 km/s. People do not generally feel the P waves, but animals seem to be sensitive to them. If a person reports that her dog started barking 20 seconds "before the earthquake," then approximately how far was the origin of the earthquake?

Accepted Answer

A)  100 km 
B)  200 km 
C)  300 km 
D)  400 km 
E)  500 km 
A)  100 km 
B)  200 km 
C)  300 km 
D)  400 km 
E)  500 km

Question 10

A certain glass window reduces the intensity level of the sound from 72 dB to 47 dB. By what factor is the acoustic power reduced by this glass window?

Accepted Answer

A)  3.2 × 10-3 
B)  2.2 × 10-2 
C)  5.6 × 10-2 
D)  1.0 × 10-1 
E)  1.5 × 10-1 
A)  3.2 × 10-3 
B)  2.2 × 10-2 
C)  5.6 × 10-2 
D)  1.0 × 10-1 
E)  1.5 × 10-1

Question 11

What are the wavelength (in meters) and frequency (in hertz) of a wave whose displacement is given by the equation y = 0.5 sin(0.20x + 120t), where x and y are in meters and t is in seconds?

Accepted Answer

A)  10 m, 0.50 Hz 
B)  5.0 m, 10 Hz 
C)  19 m, 120 Hz 
D)  31 m, 19 Hz 
E)  0.20 m, 120 $\sqrt { 2 \pi }$ Hz 
A)  10 m, 0.50 Hz 
B)  5.0 m, 10 Hz 
C)  19 m, 120 Hz 
D)  31 m, 19 Hz 
E)  0.20 m, 120 $\sqrt { 2 \pi }$ Hz

Question 12

As you are moving very quickly toward a speaker emitting a pure tone, which characteristics of the sound get larger? (There may be more than one correct choice.)

Accepted Answer

A)  frequency 
B)  amplitude 
C)  wavelength 
D)  period 
E)  loudness 
A)  frequency 
B)  amplitude 
C)  wavelength 
D)  period 
E)  loudness

Question 13

Light from a laser forms a 1.31-mm diameter spot on a wall. If the light intensity in the spot is $1.58 \times 10^4 \mathrm {~W} / \mathrm { m } ^ { 2 }$ what is the power output of the laser? Assume that all the light emitted by the laser hits the spot.

Accepted Answer

A)  21.3 mW 
B)  13.2 mW 
C)  17.9 mW 
D)  24.7 mW 
A)  21.3 mW 
B)  13.2 mW 
C)  17.9 mW 
D)  24.7 mW

Question 14

The intensity of the waves from a point source at a distance d from the source is I. What is the intensity at a distance 2d from the source?

Accepted Answer

A)  4I 
B)  2I 
C)  I/2 
D)  I/4 
E)  I/ $\sqrt { 2 }$ 
A)  4I 
B)  2I 
C)  I/2 
D)  I/4 
E)  I/ $\sqrt { 2 }$

Exam 15: Traveling Waves and Sound

Which one of the curves shown in the figure best represents the variation of wave speed v as a function of tension for transverse waves on a stretched string?

A 1.1-kg uniform bar of metal is 0.40 m long and has a diameter of 2.0 cm. When someone bangs one end of this bar, a 1.5 MHz shock wave is travels along the length of the bar and reaches the other end in 0.12 ms. What is the wavelength of the shock wave in the metal?

The speed of sound in steel is 5000 m/s. What is the wavelength of a sound wave of frequency 660 Hz660 \mathrm {~Hz}660 Hz in steel?

A certain siren radiates sound uniformly in all directions. At a distance of 17 m from the siren, the intensity level is 49 db. How many watts of power does this siren put out? The threshold of human hearing is 1.0 × 10-12 W/m2.

Sonar is used to determine the speed of an object. A 40.0-kHz signal is sent out, and a 42.0-kHz signal is returned. If the speed of sound is 345 m/s, how fast is the object moving?

Transverse waves travel at 43.2 m/s43.2 \mathrm {~m} / \mathrm { s }43.2 m/s in a string that is subjected to a tension of 60.5 N60.5 \mathrm {~N}60.5 N If the string is 15.9 m15.9 \mathrm {~m}15.9 m long, what is its mass?

The average intensity of sunlight impinging on Earth is measured to be about 1.4 kW/m2. What is the power of sunlight emitted by the sun? (Earth-Sun distance = 1.5 × 108 km, Earth radius = 6.4 × 103 km)

A certain glass window reduces the intensity level of the sound from 72 dB to 47 dB. By what factor is the acoustic power reduced by this glass window?

What are the wavelength (in meters) and frequency (in hertz) of a wave whose displacement is given by the equation y = 0.5 sin(0.20x + 120t), where x and y are in meters and t is in seconds?

As you are moving very quickly toward a speaker emitting a pure tone, which characteristics of the sound get larger? (There may be more than one correct choice.)

Light from a laser forms a 1.31-mm diameter spot on a wall. If the light intensity in the spot is 1.58×104 W/m21.58 \times 10^4 \mathrm {~W} / \mathrm { m } ^ { 2 }1.58×104 W/m2 what is the power output of the laser? Assume that all the light emitted by the laser hits the spot.

The intensity of the waves from a point source at a distance d from the source is I. What is the intensity at a distance 2d from the source?

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The speed of sound in steel is 5000 m/s. What is the wavelength of a sound wave of frequency $660 \mathrm {~Hz}$ in steel?

A certain siren radiates sound uniformly in all directions. At a distance of 17 m from the siren, the intensity level is 49 db. How many watts of power does this siren put out? The threshold of human hearing is 1.0 × 10^-12 W/m².

Transverse waves travel at $43.2 \mathrm {~m} / \mathrm { s }$ in a string that is subjected to a tension of $60.5 \mathrm {~N}$ If the string is $15.9 \mathrm {~m}$ long, what is its mass?

The average intensity of sunlight impinging on Earth is measured to be about 1.4 kW/m². What is the power of sunlight emitted by the sun? (Earth-Sun distance = 1.5 × 10⁸ km, Earth radius = 6.4 × 10³ km)

Light from a laser forms a 1.31-mm diameter spot on a wall. If the light intensity in the spot is $1.58 \times 10^4 \mathrm {~W} / \mathrm { m } ^ { 2 }$ what is the power output of the laser? Assume that all the light emitted by the laser hits the spot.