Question 1

A wave pulse on a string whose end is fixed is reflected without inversion.

Accepted Answer

A) True 
 B)False

Question 2

In a resonating pipe which is open at one end and closed at the other, 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. 
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 3

A harmonic wave has a wavelength of 2.0 m and a frequency of 5.0 Hz. What is the speed of the wave?

Accepted Answer

A)  10 m/s 
B)  0.40 m/s 
C)  0.50 m/s 
D)  0.10 m/s 
E)  2.5 m/s 
A)  10 m/s 
B)  0.40 m/s 
C)  0.50 m/s 
D)  0.10 m/s 
E)  2.5 m/s

Question 4

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 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 5

You are driving along a highway at 25.0 m/s when you hear the siren of an emergency vehicle traveling 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 6

The reason that you do not observe a Doppler shift when you listen to the car radio while driving is that

Accepted Answer

A)  the source and observer are moving at the same speed. 
B)  the air inside the car is moving at the same speed as the car. 
C)  the speed of the car is too slow compared to the speed of sound. 
D)  the speed of the car is too fast compared to the speed of sound. 
E)  there is a Doppler shift but we don't notice it. 
A)  the source and observer are moving at the same speed. 
B)  the air inside the car is moving at the same speed as the car. 
C)  the speed of the car is too slow compared to the speed of sound. 
D)  the speed of the car is too fast compared to the speed of sound. 
E)  there is a Doppler shift but we don't notice it.

Question 7

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 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 are inverted. 
E)  It is impossible to predict. 
A)  Both 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 are inverted. 
E)  It is impossible to predict.

Question 8

The lowest tone to resonate in an open pipe of length L is 200 Hz. Which one of the following frequencies will not resonate in the same pipe?

Accepted Answer

A)  200 Hz 
B)  400 Hz 
C)  600 Hz 
D)  800 Hz 
E)  900 Hz 
A)  200 Hz 
B)  400 Hz 
C)  600 Hz 
D)  800 Hz 
E)  900 Hz

Question 9

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 air is 343 m/s.

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

Question 10

Car 1 moves toward car 2 with speed v. An observer in car 2 measures the frequency of the sound emitted by car 1's horn to be f. Now, car 1 remains stationary while car 2 moves toward car 1 with speed v. The observer in car 2 now measures the frequency of car 1's horn to be f'. The relationship between the observed frequencies is

Accepted Answer

A)  f  f'. 
A)  f  f'.

Question 11

Bats use infrasound to navigate.

Accepted Answer

A) True 
 B)False

Question 12

Four waves are described by the following expressions, where distances are measured in meters and times in seconds. I y = 0.12 cos(3x - 21t)
II y = 0.15 sin(6x + 42t)
III y = 0.13 cos(6x + 21t)
IV y = -0.23 sin(3x - 42t)
Which of these waves travel in the +x direction?

Accepted Answer

A)  I and II 
B)  I and III 
C)  II and IV 
D)  I and IV 
E)  II and III 
A)  I and II 
B)  I and III 
C)  II and IV 
D)  I and IV 
E)  II and III

Question 13

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.
(a) What is the closest distance from the wall the person can stand and hear constructive interference?
(b) What is the closest distance from the wall the person can stand and hear destructive interference?

Accepted Answer

(a)0.729 m

Question 14

You are driving along a highway at 25 m/s when you hear the siren of an emergency vehicle traveling 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 15

Consider an open pipe of length L. What are the wavelengths of the three lowest tones produced by this pipe?

Accepted Answer

A)  16L, 4L, L 
B)  4L, 2L, L 
C)  2L, L, L/2 
D)  2L, L, 2L/3 
E)  4L, 4L/3, 4L/5 
A)  16L, 4L, L 
B)  4L, 2L, L 
C)  2L, L, L/2 
D)  2L, L, 2L/3 
E)  4L, 4L/3, 4L/5

Question 16

The pitch of a sound is determined by

Accepted Answer

A)  the amplitude. 
B)  the speed. 
C)  the frequency. 
D)  the wavelength. 
E)  none of the above 
A)  the amplitude. 
B)  the speed. 
C)  the frequency. 
D)  the wavelength. 
E)  none of the above

Question 17

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 period of the wave?

Accepted Answer

A)  7.22 s 
B)  1.93 s 
C)  0.870 s 
D)  0.308 s 
E)  0.139 s 
A)  7.22 s 
B)  1.93 s 
C)  0.870 s 
D)  0.308 s 
E)  0.139 s

Question 18

A crying baby emits sound with an intensity of 8.0 × 10-8 W/m2. What is the intensity level for a set of quintuplets? The lowest detectable intensity is 1.0 × 10-12 W/m2.

Accepted Answer

A)  79 dB 
B)  69 dB 
C)  56 dB 
D)  49 dB 
E)  36 dB 
A)  79 dB 
B)  69 dB 
C)  56 dB 
D)  49 dB 
E)  36 dB

Question 19

What is the wave speed in a brass wire with a radius of 0.500 mm stretched with a tension of 125 N? The density of brass is 8.60 × 103 kg/m3.

Accepted Answer

A)  0.121 m/s 
B)  100 m/s 
C)  136 m/s 
D)  500 m/s 
E)  68.8 m/s 
A)  0.121 m/s 
B)  100 m/s 
C)  136 m/s 
D)  500 m/s 
E)  68.8 m/s

Question 20

The lowest tone to resonate in a closed pipe of length L is 200 Hz. Which of the following frequencies will not resonate in that pipe?

Accepted Answer

A)  200 Hz 
B)  400 Hz 
C)  600 Hz 
D)  1000 Hz 
E)  1400 Hz 
A)  200 Hz 
B)  400 Hz 
C)  600 Hz 
D)  1000 Hz 
E)  1400 Hz

Exam 14: Waves and Sound

A wave pulse on a string whose end is fixed is reflected without inversion.

In a resonating pipe which is open at one end and closed at the other, there

A harmonic wave has a wavelength of 2.0 m and a frequency of 5.0 Hz. What is the speed of the wave?

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 air is 343 m/s.

The reason that you do not observe a Doppler shift when you listen to the car radio while driving is that

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?

The lowest tone to resonate in an open pipe of length L is 200 Hz. Which one of the following frequencies will not resonate in the same pipe?

Bats use infrasound to navigate.

Four waves are described by the following expressions, where distances are measured in meters and times in seconds. I y = 0.12 cos(3x - 21t) II y = 0.15 sin(6x + 42t) III y = 0.13 cos(6x + 21t) IV y = -0.23 sin(3x - 42t) Which of these waves travel in the +x direction?

Consider an open pipe of length L. What are the wavelengths of the three lowest tones produced by this pipe?

The pitch of a sound is determined by

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 period of the wave?

A crying baby emits sound with an intensity of 8.0 × 10-8 W/m2. What is the intensity level for a set of quintuplets? The lowest detectable intensity is 1.0 × 10-12 W/m2.

What is the wave speed in a brass wire with a radius of 0.500 mm stretched with a tension of 125 N? The density of brass is 8.60 × 103 kg/m3.

The lowest tone to resonate in a closed pipe of length L is 200 Hz. Which of the following frequencies will not resonate in that pipe?

Introduction to Physics

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Vectors in Physics

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Newtons Laws of Motion

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Linear Momentum and Collisions

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Magnetism

Magnetic Flux and Faradays Law of Induction

Alternating-Current Circuits

Electromagnetic Waves

Geometrical Optics

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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 period of the wave?

A crying baby emits sound with an intensity of 8.0 × 10^-8 W/m². What is the intensity level for a set of quintuplets? The lowest detectable intensity is 1.0 × 10^-12 W/m².

What is the wave speed in a brass wire with a radius of 0.500 mm stretched with a tension of 125 N? The density of brass is 8.60 × 10³ kg/m³.