Question 1

The lowest-pitch tone to resonate in a pipe of length L that is open at both ends is 200 Hz. Which one of the following frequencies will NOT resonate in the same pipe?

Accepted Answer

A)  400 Hz 
B)  600 Hz 
C)  800 Hz 
D)  900 Hz 
E)  1000 Hz 
A)  400 Hz 
B)  600 Hz 
C)  800 Hz 
D)  900 Hz 
E)  1000 Hz D

Question 2

Two in-phase loudspeakers that emit sound with the same frequency are placed along a wall and are separated by a distance of 8.00 m. A person is standing 12.0 m away from the wall, equidistant from the loudspeakers. When the person moves 3.00 m parallel to the wall, she experiences destructive interference for the second time. What is the frequency of the sound? The speed of sound in the room is 343 m/s. CAREFUL! The distance to the wall is NOT much greater than the distance between the speakers.

Accepted Answer

A)  278 Hz 
B)  422 Hz 
C)  452 Hz 
D)  562 Hz 
E)  694 Hz 
A)  278 Hz 
B)  422 Hz 
C)  452 Hz 
D)  562 Hz 
E)  694 Hz A

Question 3

A 1.30-m long gas column that is open at one end and closed at the other end has a fundamental resonant frequency 80.0 Hz. What is the speed of sound in this gas?

Accepted Answer

A)  104 m/s 
B)  61.5 m/s 
C)  26.0 m/s 
D)  246 m/s 
E)  416 m/s 
A)  104 m/s 
B)  61.5 m/s 
C)  26.0 m/s 
D)  246 m/s 
E)  416 m/s E

Question 4

A 1.0-g string that is 0.64 m long is fixed at both ends and is under tension. This string produces a 100-Hz tone when it vibrates in the third harmonic. The speed of sound in air is 344 m/s. The tension in the string, in is closest to

Accepted Answer

A)  2.8 N. 
B)  2.3 N. 
C)  1.8 N. 
D)  3.4 N. 
E)  3.9 N. 
A)  2.8 N. 
B)  2.3 N. 
C)  1.8 N. 
D)  3.4 N. 
E)  3.9 N.

Question 5

A guitar string is fixed at both ends. If you tighten it to increase its tension

Accepted Answer

A)  the frequencies of its vibrational modes will increase but its wavelengths will not be affected. 
B)  the wavelength increases but the frequency is not affected. 
C)  both the frequency and the wavelength increase. 
A)  the frequencies of its vibrational modes will increase but its wavelengths will not be affected. 
B)  the wavelength increases but the frequency is not affected. 
C)  both the frequency and the wavelength increase.

Question 6

One of the harmonics of a column of air open at one end and closed at the other has a frequency of 448 Hz and the next higher harmonic has a frequency of 576 Hz. What is the fundamental frequency of the air column?

Accepted Answer

A)  32 Hz 
B)  64 Hz 
C)  88 Hz 
D)  128 Hz 
E)  256 Hz 
A)  32 Hz 
B)  64 Hz 
C)  88 Hz 
D)  128 Hz 
E)  256 Hz

Question 7

A heavy stone of mass m is hung from the ceiling by a thin 8.25-g wire that is 65.0 cm long. When you gently pluck the upper end of the wire, a pulse travels down the wire and returns 7.84 ms later, having reflected off the lower end. The speed of sound in the room is 344 m/s, and the stone is heavy enough to prevent the lower end of the wire from moving. If the wire is vibrating in its second overtone, what is the wavelength of the sound it will produce?

Accepted Answer

A)  0.217 m 
B)  0.433 m 
C)  0.650 m 
D)  0.899 m 
E)  1.35 m 
A)  0.217 m 
B)  0.433 m 
C)  0.650 m 
D)  0.899 m 
E)  1.35 m

Question 8

A platinum wire that is 1.20 m long has a radius of 0.500 mm and is fixed at both ends. In its third harmonic it vibrates at 512 Hz. The density of platinum is 21.4 × 103 kg/m3. What is the tension in the wire?

Accepted Answer

A)  4.00 kN 
B)  2.00 kN 
C)  2.82 kN 
D)  1.41 kN 
E)  1.00 kN 
A)  4.00 kN 
B)  2.00 kN 
C)  2.82 kN 
D)  1.41 kN 
E)  1.00 kN

Question 9

A thin 2.00-m string of mass 50.0 g is fixed at both ends and under a tension of 70.0 N. If it is set into small-amplitude oscillation, what is the frequency of the first harmonic mode?

Accepted Answer

A)  6.61 Hz 
B)  13.2 Hz 
C)  26.5 Hz 
D)  52.9 Hz 
A)  6.61 Hz 
B)  13.2 Hz 
C)  26.5 Hz 
D)  52.9 Hz

Question 10

Two harmonic sound waves reach an observer simultaneously. The observer hears the sound intensity rise and fall with a time of 0.200 s between the maximum intensity and the succeeding minimum intensity. What is the difference in frequency of the two sound waves?

Accepted Answer

A)  10.0 Hz 
B)  0.200 Hz 
C)  5.00 Hz 
D)  2.50 Hz 
E)  1.25 Hz 
A)  10.0 Hz 
B)  0.200 Hz 
C)  5.00 Hz 
D)  2.50 Hz 
E)  1.25 Hz

Question 11

A pipe that is 120 cm long resonates to produce sound of wavelengths 480 cm, 160 cm, and 96 cm but does not resonate at any wavelengths longer than these. This pipe is

Accepted Answer

A)  open at both ends. 
B)  open at one end and closed at the other end. 
C)  closed at both ends. 
D)  We cannot tell because we do not know the frequency of the sound. 
A)  open at both ends. 
B)  open at one end and closed at the other end. 
C)  closed at both ends. 
D)  We cannot tell because we do not know the frequency of the sound.

Question 12

A heavy stone of mass m is hung from the ceiling by a thin 8.25-g wire that is 65.0 cm long. When you gently pluck the upper end of the wire, a pulse travels down the wire and returns 7.84 ms later, having reflected off the lower end. The speed of sound in the room is 344 m/s, and the stone is heavy enough to prevent the lower end of the wire from moving. If the wire is vibrating in its second overtone, what is the frequency of the sound it will produce?

Accepted Answer

A)  128 Hz 
B)  191 Hz 
C)  255 Hz 
D)  383 Hz 
E)  765 Hz 
A)  128 Hz 
B)  191 Hz 
C)  255 Hz 
D)  383 Hz 
E)  765 Hz

Question 13

A wave pulse traveling to the right along a thin cord reaches a discontinuity where the rope becomes thicker and heavier. What is the orientation of the reflected and transmitted pulses?

Accepted Answer

A)  Both pulses are right side up. 
B)  The reflected pulse returns right side up while the transmitted pulse is inverted. 
C)  The reflected pulse returns inverted while the transmitted pulse is right side up. 
D)  Both pulses are inverted. 
A)  Both pulses are right side up. 
B)  The reflected pulse returns right side up while the transmitted pulse is inverted. 
C)  The reflected pulse returns inverted while the transmitted pulse is right side up. 
D)  Both pulses are inverted.

Question 14

An organ pipe open at both ends has two successive harmonics with frequencies of 210 Hz and 240 Hz. What is the length of the pipe? The speed of sound is 344 m/s in air.

Accepted Answer

A)  5.25 m 
B)  5.73 m 
C)  2.76 m 
D)  4.90 m 
E)  3.62 m 
A)  5.25 m 
B)  5.73 m 
C)  2.76 m 
D)  4.90 m 
E)  3.62 m

Question 15

Two strings of identical material and radius are stretched with the same tension with their ends fixed, but one string is 8.0 mm longer than the other. Waves on these strings propagate at 420 m/s. The fundamental frequency of the longer string is 528 Hz. What is the beat frequency when each string is vibrating at its fundamental frequency?

Accepted Answer

A)  22 Hz 
B)  11 Hz 
C)  16 Hz 
D)  5.5 Hz 
E)  27 Hz 
A)  22 Hz 
B)  11 Hz 
C)  16 Hz 
D)  5.5 Hz 
E)  27 Hz

Question 16

Two identical loudspeakers that are 5.00 m apart and face toward each other are driven in phase by the same oscillator at a frequency of 875 Hz. The speed of sound in the room is 344 m/s. If you start out standing midway between the speakers, find the shortest distance you can walk toward either speaker in order to hear a minimum of sound.

Accepted Answer

A)  0.0983 m 
B)  0.197 m 
C)  0.295 m 
D)  0.393 m 
E)  0.590 m 
A)  0.0983 m 
B)  0.197 m 
C)  0.295 m 
D)  0.393 m 
E)  0.590 m

Question 17

A wave pulse traveling to the right along a thin cord reaches a discontinuity where the rope becomes thinner and lighter. What is the orientation of the reflected and transmitted pulses?

Accepted Answer

A)  Both pulses are right side up. 
B)  The reflected pulse returns right side up while the transmitted pulse is inverted. 
C)  The reflected pulse returns inverted while the transmitted pulse is right side up. 
D)  Both pulses are inverted. 
A)  Both pulses are right side up. 
B)  The reflected pulse returns right side up while the transmitted pulse is inverted. 
C)  The reflected pulse returns inverted while the transmitted pulse is right side up. 
D)  Both pulses are inverted.

Question 18

An airplane flying faster than the speed of sound of 340 m/s produces a shock wave that makes an angle of 50° with the direction the plane is flying. What is the speed of the plane?

Accepted Answer

A)  490 m/s 
B)  530 m/s 
C)  390 m/s 
D)  440 m/s 
E)  405 m/s 
A)  490 m/s 
B)  530 m/s 
C)  390 m/s 
D)  440 m/s 
E)  405 m/s

Question 19

A string, 0.28 m long and vibrating in its third harmonic, excites an open pipe that is 0.82 m long into its second overtone resonance. The speed of sound in air is 345 m/s. The speed of transverse waves on the string is closest to

Accepted Answer

A)  120 m/s. 
B)  110 m/s. 
C)  100 m/s. 
D)  98 m/s. 
E)  91 m/s. 
A)  120 m/s. 
B)  110 m/s. 
C)  100 m/s. 
D)  98 m/s. 
E)  91 m/s.

Question 20

Standing waves of frequency 57 Hz are produced on a string that has mass per unit length 0.0160 kg/m. With what tension must the string be stretched between two supports if adjacent nodes in the standing wave are to be 0.71 meters apart?

Accepted Answer

The answer of Standing waves of frequency 57 Hz are...

Exam 17: Superposition

The lowest-pitch tone to resonate in a pipe of length L that is open at both ends is 200 Hz. Which one of the following frequencies will NOT resonate in the same pipe?

A 1.30-m long gas column that is open at one end and closed at the other end has a fundamental resonant frequency 80.0 Hz. What is the speed of sound in this gas?

A 1.0-g string that is 0.64 m long is fixed at both ends and is under tension. This string produces a 100-Hz tone when it vibrates in the third harmonic. The speed of sound in air is 344 m/s. The tension in the string, in is closest to

A guitar string is fixed at both ends. If you tighten it to increase its tension

One of the harmonics of a column of air open at one end and closed at the other has a frequency of 448 Hz and the next higher harmonic has a frequency of 576 Hz. What is the fundamental frequency of the air column?

A platinum wire that is 1.20 m long has a radius of 0.500 mm and is fixed at both ends. In its third harmonic it vibrates at 512 Hz. The density of platinum is 21.4 × 103 kg/m3. What is the tension in the wire?

A thin 2.00-m string of mass 50.0 g is fixed at both ends and under a tension of 70.0 N. If it is set into small-amplitude oscillation, what is the frequency of the first harmonic mode?

Two harmonic sound waves reach an observer simultaneously. The observer hears the sound intensity rise and fall with a time of 0.200 s between the maximum intensity and the succeeding minimum intensity. What is the difference in frequency of the two sound waves?

A pipe that is 120 cm long resonates to produce sound of wavelengths 480 cm, 160 cm, and 96 cm but does not resonate at any wavelengths longer than these. This pipe is

A wave pulse traveling to the right along a thin cord reaches a discontinuity where the rope becomes thicker and heavier. What is the orientation of the reflected and transmitted pulses?

An organ pipe open at both ends has two successive harmonics with frequencies of 210 Hz and 240 Hz. What is the length of the pipe? The speed of sound is 344 m/s in air.

A wave pulse traveling to the right along a thin cord reaches a discontinuity where the rope becomes thinner and lighter. What is the orientation of the reflected and transmitted pulses?

An airplane flying faster than the speed of sound of 340 m/s produces a shock wave that makes an angle of 50° with the direction the plane is flying. What is the speed of the plane?

A string, 0.28 m long and vibrating in its third harmonic, excites an open pipe that is 0.82 m long into its second overtone resonance. The speed of sound in air is 345 m/s. The speed of transverse waves on the string is closest to

Standing waves of frequency 57 Hz are produced on a string that has mass per unit length 0.0160 kg/m. With what tension must the string be stretched between two supports if adjacent nodes in the standing wave are to be 0.71 meters apart?

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A platinum wire that is 1.20 m long has a radius of 0.500 mm and is fixed at both ends. In its third harmonic it vibrates at 512 Hz. The density of platinum is 21.4 × 10³ kg/m³. What is the tension in the wire?