Question 1

Standing sound waves: In a resonating pipe that is open at one end and closed at the other end, there

Accepted Answer

A)  are displacement nodes at each end. 
B)  are displacement antinodes at each end. 
C)  is a displacement node at the open end and a displacement antinode at the closed end. 
D)  is a displacement node at the closed end and a displacement antinode at the open end.

Question 2

Standing sound waves: In a resonating pipe that is open at both ends, there

Accepted Answer

A)  are displacement nodes at each end. 
B)  are displacement antinodes at each end. 
C)  is a displacement node at one end and a displacement antinode at the other end. 
D)  None of the above are possible.

Question 3

Mathematics of traveling waves: The figure shows the displacement y of a traveling wave at a given position as a function of time and the displacement of the same wave at a given time as a function of position. Determine the wavelength of the wave.

Accepted Answer

A)  2.0 cm 
B)  3.0 m 
C)  2.0 m 
D)  4.0 m 
E)  1.5 m

Question 4

Standing waves on a string: 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

Question 5

Standing sound waves: 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

Question 6

Standing waves on a string: 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

Question 7

Standing waves on a string: 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.

Question 8

Beats: 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

Question 9

Doppler effect: You are driving along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind and you perceive the frequency as 1310 Hz. You are relieved that he is in pursuit of a different speeder when he continues past you, but now you perceive the frequency as 1240 Hz. What is the frequency of the siren in the police car? The speed of sound in air is 343 m/s.

Accepted Answer

A)  1300 Hz 
B)  1320 Hz 
C)  1270 Hz 
D)  1360 Hz 
E)  1370 Hz

Question 10

Waves on a string: 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 stone is heavy enough to prevent the lower end of the wire from moving. What is the mass m of the stone?

Accepted Answer

A)  8.90 kg 
B)  23.1 kg 
C)  35.6 kg 
D)  227 kg 
E)  349 kg

Question 11

Waves on a string: You are generating traveling waves on a stretched string by wiggling one end. If you suddenly begin to wiggle more rapidly without appreciably affecting the tension, you will cause the waves to move down the string

Accepted Answer

A)  faster than before. 
B)  slower than before. 
C)  at the same speed as before.

Question 12

Waves on a string: In the figure, which of the curves best represents the variation of wave speed as a function of tension for transverse waves on a stretched string?

Accepted Answer

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

Question 13

Sound level: If the intensity level at distance d of one trombone is 70 dB, what is the intensity level of 76 identical trombones, all at distance d?

Accepted Answer

A)  146 dB 
B)  89 dB 
C)  5320 dB 
D)  76 dB 
E)  82 dB

Question 14

Standing waves on a string: A standing wave is oscillating at 690 Hz on a string, as shown in the figure. What is the speed of traveling waves on this string?

Accepted Answer

A)  280 m/s 
B)  410 m/s 
C)  210 m/s 
D)  140 m/s

Question 15

Mathematics of traveling waves: You and your surfing buddy are waiting to catch a wave a few hundred meters off the beach. The waves are conveniently sinusoidal, and you notice that when you're on the top of one wave and moving toward your friend, she is exactly halfway between you and the trough of the wave. 1.50 seconds later, your friend is at the top of the wave. You estimate the horizontal distance between you and your friend at 8.00 m.
(a) What is the frequency of the waves?
(b) Find the speed of the waves.

Accepted Answer

The answer of Mathematics of traveling waves: You and your...

Question 16

Doppler effect: A carousel that is 5.00 m in radius has a pair of 600-Hz sirens mounted on posts at opposite ends of a diameter. The carousel rotates with an angular velocity of 0.800 rad/s. A stationary listener is located at a distance from the carousel. The speed of sound is 350 m/s. The maximum beat frequency of the sirens at the position of the listener is closest to

Accepted Answer

A)  6 Hz. 
B)  8 Hz. 
C)  10 Hz. 
D)  12 Hz. 
E)  14 Hz.

Question 17

Shock waves: Shock waves occur when

Accepted Answer

A)  the frequency of the waves is the resonant frequency of the system. 
B)  the amplitude of waves exceeds the critical shock value. 
C)  two waves from different sources collide with each other. 
D)  the wave source is traveling at a speed greater than the wave speed. 
E)  the period of the waves matches the lifetime of the waves.

Question 18

Standing sound waves: A pipe that is 0.46 m long and open at both ends vibrates in the second overtone with a frequency of  In this situation, the distance from the center of the pipe to the nearest antinode is closest to

Accepted Answer

A)  7.7 cm. 
B)  3.8 cm. 
C)  12 cm. 
D)  15 cm. 
E)  zero.

Question 19

Standing waves on a string: 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

Question 20

Doppler effect: A boy on a bicycle approaches a brick wall as he sounds his horn at a frequency 400.00 Hz. The sound he hears reflected back from the wall is at a frequency 408.00 Hz. At what is the speed is the boy riding his bicycle toward the wall? Assume the speed of sound in air is 340 m/s.

Accepted Answer

A)  3.68 m/s 
B)  333 m/s 
C)  6.67 m/s 
D)  6.80 m/s 
E)  3.37 m/s

Exam 14: Periodic Motion