Question 1

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 2

If the intensity level of one trombone is 70 dB,calculate a reasonable estimate for the intensity level of 76 trombones all playing simultaneously in the same place?

Accepted Answer

A) 146 dB 
B) 89 dB 
C) 70 dB 
D) 76 dB 
E) 82 dB 
A) 146 dB 
B) 89 dB 
C) 70 dB 
D) 76 dB 
E) 82 dB

Question 3

A 0.588-m string is tightly clamped at both ends.If the lowest standing wave frequency of the string is $$326 \mathrm {~Hz}$$ how fast do waves travel on this string?

Accepted Answer

A) 383 m/s 
B) 475 m/s 
C) 582 m/s 
D) 724 m/s 
A) 383 m/s 
B) 475 m/s 
C) 582 m/s 
D) 724 m/s

Question 4

Find the first three harmonics of a string of linear mass density 2.00 g/m and length 0.600 m when the tension in it is 50.0 N.

Accepted Answer

A) 132 Hz, 264 Hz, 395 Hz 
B) 66 Hz, 132 Hz, 198 Hz 
C) 264 Hz, 528 Hz, 792 Hz 
D) none of the above 
A) 132 Hz, 264 Hz, 395 Hz 
B) 66 Hz, 132 Hz, 198 Hz 
C) 264 Hz, 528 Hz, 792 Hz 
D) none of the above

Question 5

Standing waves of frequency 17 Hz are produced on a string that has a mass per unit length of $$0.0160 \mathrm {~kg} / \mathrm { m } .$$ To what tension must the string be stretched between two supports if adjacent nodes in the standing wave are to be 0.87 m apart?

Accepted Answer

The answer of Standing waves of frequency 17 Hz are...

Question 6

Seven seconds after a brilliant flash of lightning,thunder shakes the house.Approximately how far was the lightning strike from the house?

Accepted Answer

A) much closer than one kilometer 
B) about one kilometer away 
C) about two kilometers away 
D) much farther away than two kilometers 
E) It is impossible to say. 
A) much closer than one kilometer 
B) about one kilometer away 
C) about two kilometers away 
D) much farther away than two kilometers 
E) It is impossible to say.

Question 7

You double your distance from a sound source that is radiating equally in all directions.What happens to the intensity level of the sound? It drops by

Accepted Answer

A) 2 dB. 
B) 3 dB. 
C) 6 dB. 
D) 8 dB. 
A) 2 dB. 
B) 3 dB. 
C) 6 dB. 
D) 8 dB.

Question 8

The sound intensity level 5.0 m from a point source is 95 dB.At what distance will it be 75 dB?

Accepted Answer

A) 25 m 
B) 50 m 
C) 75 m 
D) 225 m 
A) 25 m 
B) 50 m 
C) 75 m 
D) 225 m

Question 9

A car approaches you at a constant speed,sounding its horn,and you hear a frequency of 76 Hz.After the car goes by,you hear a frequency of 65 Hz.What is the frequency of the sound emitted by the horn? The speed of sound in the air is 343 m/s.

Accepted Answer

A) 68 Hz 
B) 69 Hz 
C) 70 Hz 
D) 71 Hz 
E) 72 Hz 
A) 68 Hz 
B) 69 Hz 
C) 70 Hz 
D) 71 Hz 
E) 72 Hz

Question 10

Two taut strings of identical mass and length are stretched with their ends fixed,but the tension in one string is 1.10 times greater than in the other.Waves on the string with the lower tension propagate at 35.2 m/s.The fundamental frequency of that string is 258 Hz.What is the beat frequency when each string is vibrating at its fundamental frequency?

Accepted Answer

A) 11.0 Hz 
B) 9.00 Hz 
C) 13.7 Hz 
D) 12.6 Hz 
E) 17.1 Hz 
A) 11.0 Hz 
B) 9.00 Hz 
C) 13.7 Hz 
D) 12.6 Hz 
E) 17.1 Hz

Question 11

A 4.0-g string is 0.36 m long and is under tension.The string vibrates at 500 Hz in its third harmonic.What is the wavelength of the standing wave in the string?

Accepted Answer

A) 0.24 m 
B) 0.36 m 
C) 0.54 m 
D) 0.72 m 
E) 0.90 m 
A) 0.24 m 
B) 0.36 m 
C) 0.54 m 
D) 0.72 m 
E) 0.90 m

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

You are driving along a highway at 25.0 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 frequency of the siren? The speed of sound in air is 343 m/s.

Accepted Answer

A) 1850 Hz 
B) 2000 Hz 
C) 2050 Hz 
D) 2010 Hz 
E) 1980 Hz 
A) 1850 Hz 
B) 2000 Hz 
C) 2050 Hz 
D) 2010 Hz 
E) 1980 Hz

Question 14

Two taut strings of identical mass per unit length are stretched with the same tension with their ends fixed,but one string is 0.330 cm longer than the other.Waves on these strings propagate at 34.0 m/s.The fundamental frequency of the shorter string is 258 Hz.What is the beat frequency when each string is vibrating at its fundamental frequency?

Accepted Answer

A) 12.3 Hz 
B) 9.00 Hz 
C) 12.0 Hz 
D) 12.7 Hz 
E) 11.3 Hz 
A) 12.3 Hz 
B) 9.00 Hz 
C) 12.0 Hz 
D) 12.7 Hz 
E) 11.3 Hz

Question 15

Two tuning forks have frequencies of 440 and 522 Hz.What is the beat frequency if both are sounding simultaneously?

Accepted Answer

A) 962 Hz 
B) 481 Hz 
C) 82 Hz 
D) 55 Hz 
E) 41 Hz 
A) 962 Hz 
B) 481 Hz 
C) 82 Hz 
D) 55 Hz 
E) 41 Hz

Question 16

A crane lifts a 2500-kg beam using a steel cable whose mass per unit length is 0.650 kg/m.What is the speed of transverse waves on this cable if the upward acceleration of the beam is a steady 3.00 m/s2?

Accepted Answer

A) 194 m/s 
B) 578 m/s 
C) 1220 m/s 
D) 1880 m/s 
E) 222 m/s 
A) 194 m/s 
B) 578 m/s 
C) 1220 m/s 
D) 1880 m/s 
E) 222 m/s

Question 17

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 18

A factory siren indicating the end of a shift has a frequency of 80 Hz where the speed of sound in air is 343 m/s.What frequency is perceived by the occupant of a car that is traveling at 30 m/s (a)towards the factory and (b)away from the factory?

Accepted Answer

The answer of A factory siren indicating the end of...

Question 19

A 90-gram wire that is 1.0 m long is under tension.When a transverse wave of frequency 890 Hz travels down the wire,its wavelength is 0.10 m and its amplitude is 6.5 mm.What is the tension in the wire?

Accepted Answer

A) 710 N 
B) 820 N 
C) 930 N 
D) 1000 N 
E) 1100 N 
A) 710 N 
B) 820 N 
C) 930 N 
D) 1000 N 
E) 1100 N

Question 20

A policeman in a stationary car measures the speed of approaching cars by means of an ultrasonic device that emits a sound with a frequency of 39.6 kHz.A car is approaching him at a speed of 35.0 m/s.The wave is reflected by the car and interferes with the emitted sound producing beats.What is the frequency of the beats when the speed of sound in air is 343 m/s?

Accepted Answer

A) 5000 Hz 
B) 4500 Hz 
C) 8490 Hz 
D) 9000 Hz 
E) 4250 Hz 
A) 5000 Hz 
B) 4500 Hz 
C) 8490 Hz 
D) 9000 Hz 
E) 4250 Hz

Exam 21: Mechanical Waves

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?

If the intensity level of one trombone is 70 dB,calculate a reasonable estimate for the intensity level of 76 trombones all playing simultaneously in the same place?

A 0.588-m string is tightly clamped at both ends.If the lowest standing wave frequency of the string is 326 Hz326 \mathrm {~Hz}326 Hz how fast do waves travel on this string?

Find the first three harmonics of a string of linear mass density 2.00 g/m and length 0.600 m when the tension in it is 50.0 N.

Standing waves of frequency 17 Hz are produced on a string that has a mass per unit length of 0.0160 kg/m.0.0160 \mathrm {~kg} / \mathrm { m } .0.0160 kg/m. To what tension must the string be stretched between two supports if adjacent nodes in the standing wave are to be 0.87 m apart?

Seven seconds after a brilliant flash of lightning,thunder shakes the house.Approximately how far was the lightning strike from the house?

You double your distance from a sound source that is radiating equally in all directions.What happens to the intensity level of the sound? It drops by

The sound intensity level 5.0 m from a point source is 95 dB.At what distance will it be 75 dB?

A car approaches you at a constant speed,sounding its horn,and you hear a frequency of 76 Hz.After the car goes by,you hear a frequency of 65 Hz.What is the frequency of the sound emitted by the horn? The speed of sound in the air is 343 m/s.

A 4.0-g string is 0.36 m long and is under tension.The string vibrates at 500 Hz in its third harmonic.What is the wavelength of the standing wave in the string?

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.)

Two tuning forks have frequencies of 440 and 522 Hz.What is the beat frequency if both are sounding simultaneously?

A crane lifts a 2500-kg beam using a steel cable whose mass per unit length is 0.650 kg/m.What is the speed of transverse waves on this cable if the upward acceleration of the beam is a steady 3.00 m/s2?

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?

A factory siren indicating the end of a shift has a frequency of 80 Hz where the speed of sound in air is 343 m/s.What frequency is perceived by the occupant of a car that is traveling at 30 m/s (a)towards the factory and (b)away from the factory?

A 90-gram wire that is 1.0 m long is under tension.When a transverse wave of frequency 890 Hz travels down the wire,its wavelength is 0.10 m and its amplitude is 6.5 mm.What is the tension in the wire?

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Filters

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 0.588-m string is tightly clamped at both ends.If the lowest standing wave frequency of the string is $326 \mathrm {~Hz}$ how fast do waves travel on this string?

Standing waves of frequency 17 Hz are produced on a string that has a mass per unit length of $0.0160 \mathrm {~kg} / \mathrm { m } .$ To what tension must the string be stretched between two supports if adjacent nodes in the standing wave are to be 0.87 m apart?

A crane lifts a 2500-kg beam using a steel cable whose mass per unit length is 0.650 kg/m.What is the speed of transverse waves on this cable if the upward acceleration of the beam is a steady 3.00 m/s²?