Question 1

You drop a stone down a well that is 9.50 m deep. How long is it before you hear the splash? The speed of sound in air is 343 m/s.

Accepted Answer

A)  1.39 s 
B)  1.40 s 
C)  1.41 s 
D)  1.42 s 
E)  1.43 s 
A)  1.39 s 
B)  1.40 s 
C)  1.41 s 
D)  1.42 s 
E)  1.43 s

Question 2

The intensity level of a power mower at a distance of 1.0 m is 100 dB. You wake up one morning to find that four of your neighbors are mowing their lawn 20 m from your open bedroom window. What is the intensity level in your bedroom?

Accepted Answer

A)  80 dB 
B)  104 dB 
C)  400 dB 
D)  50 dB 
E)  40 dB 
A)  80 dB 
B)  104 dB 
C)  400 dB 
D)  50 dB 
E)  40 dB

Question 3

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

Accepted Answer

A)  73 Hz 
B)  75 Hz 
C)  77 Hz 
D)  79 Hz 
E)  81 Hz 
A)  73 Hz 
B)  75 Hz 
C)  77 Hz 
D)  79 Hz 
E)  81 Hz

Question 4

Two in-phase loudspeakers are 3.00 m apart. They emit sound with a frequency of 490 Hz. A microphone is placed half-way between the speakers and then moved along the line joining the two speakers until the first point of constructive interference is found. At what distance from that midpoint is that first point? The speed of sound in air is 343 m/s.

Accepted Answer

A)  0.175 m 
B)  0.350 m 
C)  0.500 m 
D)  0.700 m 
E)  There is no point in that line where constructive interference occurs. 
A)  0.175 m 
B)  0.350 m 
C)  0.500 m 
D)  0.700 m 
E)  There is no point in that line where constructive interference occurs.

Question 5

As you stand by the side of the road, 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 speed of the car? The speed of sound in air is 343 m/s.

Accepted Answer

A)  26 m/s 
B)  27 m/s 
C)  28 m/s 
D)  29 m/s 
E)  30 m/s 
A)  26 m/s 
B)  27 m/s 
C)  28 m/s 
D)  29 m/s 
E)  30 m/s

Question 6

A tsunami, an ocean wave generated by an earthquake, propagates along the open ocean at 700 km/hr and has a wavelength of 750 km. What is the frequency of the waves in such a tsunami?

Accepted Answer

A)  0.933 Hz 
B)  0.000259 Hz 
C)  1.07 Hz 
D)  6.76 Hz 
E)  0.148 Hz 
A)  0.933 Hz 
B)  0.000259 Hz 
C)  1.07 Hz 
D)  6.76 Hz 
E)  0.148 Hz

Question 7

In many cartoon shows, a character runs of a cliff, realizes his predicament and lets out a scream. He continues to scream as he falls. If the physical situation is portrayed correctly, from the vantage point of an observer at the foot of the cliff, the pitch of the scream should be

Accepted Answer

A)  higher than the original pitch and constant. 
B)  higher than the original pitch and increasing as he falls. 
C)  lower than the original pitch and constant. 
D)  lower than the original pitch and decreasing as he falls. 
E)  It is impossible to predict. 
A)  higher than the original pitch and constant. 
B)  higher than the original pitch and increasing as he falls. 
C)  lower than the original pitch and constant. 
D)  lower than the original pitch and decreasing as he falls. 
E)  It is impossible to predict.

Question 8

Two soldiers are marching side by side with a speed of 1.9 m/s, but one of them moves 92 cm for each step he takes, while the other moves only 84 cm. How often are they in step?

Accepted Answer

A)  every 3.2 s 
B)  every 8.7 s 
C)  every 4.6 s 
D)  every 5.1 s 
E)  every 10 s 
A)  every 3.2 s 
B)  every 8.7 s 
C)  every 4.6 s 
D)  every 5.1 s 
E)  every 10 s

Question 9

A factory siren indicating the end of a shift has a frequency of 80 Hz. What frequency is perceived by the occupant of a car traveling towards the factory at 30 m/s? The speed of sound in air is 343 m/s.

Accepted Answer

A)  83 Hz 
B)  85 Hz 
C)  87 Hz 
D)  89 Hz 
E)  91 Hz 
A)  83 Hz 
B)  85 Hz 
C)  87 Hz 
D)  89 Hz 
E)  91 Hz

Question 10

Two cars are traveling in the same direction and with the same speed along a straight highway. Does either driver hear a different frequency from the other car's horn than they would if the cars were stationary?

Accepted Answer

A)  Yes, they both experience a Doppler shift. 
B)  Only the driver of the front car experiences a Doppler shift. 
C)  Only the driver of the rear car experiences a Doppler shift. 
D)  No, because neither driver experiences a Doppler shift. 
E)  It is impossible to predict. 
A)  Yes, they both experience a Doppler shift. 
B)  Only the driver of the front car experiences a Doppler shift. 
C)  Only the driver of the rear car experiences a Doppler shift. 
D)  No, because neither driver experiences a Doppler shift. 
E)  It is impossible to predict.

Question 11

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)  431 Hz 
C)  82 Hz 
D)  55 Hz 
E)  41 Hz 
A)  962 Hz 
B)  431 Hz 
C)  82 Hz 
D)  55 Hz 
E)  41 Hz

Question 12

Two pure tones are sounded together and a particular beat frequency is heard. What happens to the beat frequency if the frequency of one of the tones is increased?

Accepted Answer

A)  It increases. 
B)  It decreases. 
C)  It does not change. 
D)  It becomes zero. 
E)  It could either increase or decrease. 
A)  It increases. 
B)  It decreases. 
C)  It does not change. 
D)  It becomes zero. 
E)  It could either increase or decrease.

Question 13

A bat emits a sound at a frequency of 39.0 kHz as it approaches a wall. The bat detects beats with a frequency of 827 Hz between the sound it emits and the echo bouncing from the wall. What is the speed of the bat? The speed of sound in air is 343 m/s.

Accepted Answer

A)  2.7 m/s 
B)  3.0 m/s 
C)  3.6 m/s 
D)  5.4 m/s 
E)  9.0 m/s 
A)  2.7 m/s 
B)  3.0 m/s 
C)  3.6 m/s 
D)  5.4 m/s 
E)  9.0 m/s

Question 14

A pipe of length L closed at one end is resonating at its fundamental frequency. Which statement is correct?

Accepted Answer

A)  The wavelength is 4L and there is a displacement node at the pipe's open end. 
B)  The wavelength is 4L and there is a displacement antinode at the pipe's open end. 
C)  The wavelength is L and there is a displacement node at the pipe's open end. 
D)  The wavelength is L and there is a displacement antinode at the pipe's open end. 
A)  The wavelength is 4L and there is a displacement node at the pipe's open end. 
B)  The wavelength is 4L and there is a displacement antinode at the pipe's open end. 
C)  The wavelength is L and there is a displacement node at the pipe's open end. 
D)  The wavelength is L and there is a displacement antinode at the pipe's open end.

Question 15

In a resonating pipe which 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 
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

Question 16

If the intensity level of one trombone is 70 dB, what is the intensity level of 76 trombones?

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 17

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

Question 18

Two in-phase loudspeakers are some distance apart. They emit sound with a frequency of 572 Hz. A microphone is moved between the speakers to record the wave amplitude at points along that line. What is the spacing between points where constructive interference occurs? The speed of sound in air is 343 m/s.

Accepted Answer

A)  0.300 m 
B)  0.600 m 
C)  0.900 m 
D)  1.20 m 
E)  1.50 m 
A)  0.300 m 
B)  0.600 m 
C)  0.900 m 
D)  1.20 m 
E)  1.50 m

Question 19

Two in-phase loudspeakers are placed along a wall and are separated by a distance of 4.00 m. They emit sound with a frequency of 514 Hz. A person is standing away from the wall, in front of one of the loudspeakers. What is the closest distance from the wall the person can stand and hear destructive interference? The speed of sound in air is 343 m/s.

Accepted Answer

A)  0.344 m 
B)  0.365 m 
C)  0.729 m 
D)  1.15 m 
E)  1.64 m 
A)  0.344 m 
B)  0.365 m 
C)  0.729 m 
D)  1.15 m 
E)  1.64 m

Question 20

The vertical displacement of a string is given by y(x,t) = (6.00 mm) cos[(3.25 m-1)x - (7.22 s-1)t]. What is the amplitude of the wave?

Accepted Answer

A)  6.00 mm 
B)  12.0 mm 
C)  3.00 mm 
D)  2.00 mm 
E)  None of the other choices is correct. 
A)  6.00 mm 
B)  12.0 mm 
C)  3.00 mm 
D)  2.00 mm 
E)  None of the other choices is correct.

Exam 14: Waves and Sound

You drop a stone down a well that is 9.50 m deep. How long is it before you hear the splash? The speed of sound in air is 343 m/s.

The intensity level of a power mower at a distance of 1.0 m is 100 dB. You wake up one morning to find that four of your neighbors are mowing their lawn 20 m from your open bedroom window. What is the intensity level in your bedroom?

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

As you stand by the side of the road, 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 speed of the car? The speed of sound in air is 343 m/s.

A tsunami, an ocean wave generated by an earthquake, propagates along the open ocean at 700 km/hr and has a wavelength of 750 km. What is the frequency of the waves in such a tsunami?

In many cartoon shows, a character runs of a cliff, realizes his predicament and lets out a scream. He continues to scream as he falls. If the physical situation is portrayed correctly, from the vantage point of an observer at the foot of the cliff, the pitch of the scream should be

Two soldiers are marching side by side with a speed of 1.9 m/s, but one of them moves 92 cm for each step he takes, while the other moves only 84 cm. How often are they in step?

A factory siren indicating the end of a shift has a frequency of 80 Hz. What frequency is perceived by the occupant of a car traveling towards the factory at 30 m/s? The speed of sound in air is 343 m/s.

Two cars are traveling in the same direction and with the same speed along a straight highway. Does either driver hear a different frequency from the other car's horn than they would if the cars were stationary?

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

Two pure tones are sounded together and a particular beat frequency is heard. What happens to the beat frequency if the frequency of one of the tones is increased?

A bat emits a sound at a frequency of 39.0 kHz as it approaches a wall. The bat detects beats with a frequency of 827 Hz between the sound it emits and the echo bouncing from the wall. What is the speed of the bat? The speed of sound in air is 343 m/s.

A pipe of length L closed at one end is resonating at its fundamental frequency. Which statement is correct?

In a resonating pipe which is open at both ends, there

If the intensity level of one trombone is 70 dB, what is the intensity level of 76 trombones?

The vertical displacement of a string is given by y(x,t) = (6.00 mm) cos[(3.25 m-1)x - (7.22 s-1)t]. What is the amplitude of the wave?

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The vertical displacement of a string is given by y(x,t) = (6.00 mm) cos[(3.25 m^-1)x - (7.22 s^-1)t]. What is the amplitude of the wave?