Question 1

An elephant can hear sound with a frequency of 15 Hz. What is the wavelength of this wave if the speed of sound in air is 343 m/s?

Accepted Answer

The answer of An elephant can hear sound with a...

Question 2

Find the speed of an ocean wave whose displacement is given by the equation $y = 3.7 \cos ( 2.2 x - 5.6 t )$ where x and y are in meters and t is in seconds.

Accepted Answer

A)  2.5 m/s 
B)  1.9 m/s 
C)  3.5 m/s 
D)  4.5 m/s 
A)  2.5 m/s 
B)  1.9 m/s 
C)  3.5 m/s 
D)  4.5 m/s

Question 3

A string of mass m is under tension, and the speed of a wave in the string is v. What will be the speed of a wave in the string if the mass of the string is increased to 2m but with no change in the length or tension?

Accepted Answer

A)  v/2 
B)  v/ $\sqrt { 2 }$ 
C)  v $\sqrt { 2 }$ 
D)  2v 
E)  4v 
A)  v/2 
B)  v/ $\sqrt { 2 }$ 
C)  v $\sqrt { 2 }$ 
D)  2v 
E)  4v

Question 4

A 15-m rope is pulled taut with a tension of 140 N. It takes 0.545 s for a wave to propagate along the rope. What is the mass of the rope?

Accepted Answer

A)  1.7 kg 
B)  2.1 kg 
C)  2.8 kg 
D)  5.1 kg 
E)  3.2 kg 
A)  1.7 kg 
B)  2.1 kg 
C)  2.8 kg 
D)  5.1 kg 
E)  3.2 kg

Question 5

You are driving along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind at constant speed and you perceive the frequency as 1340 ${~Hz}$ . You are relieved that he is in pursuit of a different driver when he continues past you, but now you perceive the frequency as 1300 ${~Hz}$ What is the speed of the police car? The speed of sound in air is 343$ {~m} / \mathrm { s }$

Accepted Answer

A)  38.4 m/s 
B)  30 m/s 
C)  39.2 m/s 
D)  40.1 m/s 
E)  41.7 m/s 
A)  38.4 m/s 
B)  30 m/s 
C)  39.2 m/s 
D)  40.1 m/s 
E)  41.7 m/s

Question 6

A certain factory whistle can be heard up to a distance of 2.5 km. Assuming that the acoustic output of the whistle is uniform in all directions, how much acoustic power is emitted by the whistle? The threshold of human hearing is 1.0 × 10-12 W/m2.

Accepted Answer

A)  0.079 mW 
B)  0.026 mW 
C)  0.26 mW 
D)  0.79 mW 
E)  2.6 mW 
A)  0.079 mW 
B)  0.026 mW 
C)  0.26 mW 
D)  0.79 mW 
E)  2.6 mW

Question 7

Why does the intensity of waves from a small source decrease with the square of the distance from the source?

Accepted Answer

A)  The waves run out of energy as they travel. 
B)  The waves spread out as they travel. 
C)  The medium through which the waves travel absorbs the energy of the waves. 
D)  The waves slow down as they travel away from the source. 
E)  The frequency of the waves decreases as they get farther from the source. 
A)  The waves run out of energy as they travel. 
B)  The waves spread out as they travel. 
C)  The medium through which the waves travel absorbs the energy of the waves. 
D)  The waves slow down as they travel away from the source. 
E)  The frequency of the waves decreases as they get farther from the source.

Question 8

What is the intensity of a 70-dB sound? The threshold of human hearing is 
1.0 × 10-12 W/m2.

Accepted Answer

A)  10-4 W/m2 
B)  10-5 W/m2 
C)  10-6 W/m2 
D)  10-7 W/m2 
A)  10-4 W/m2 
B)  10-5 W/m2 
C)  10-6 W/m2 
D)  10-7 W/m2

Question 9

The speed of sound through the ground is about 6.0 km/s while the speed of sound in air is 343 m/s. A very powerful explosion occurs some distance away and you feel the ground vibrate 60 seconds before you hear the sound of the explosion. How far away is the explosion?

Accepted Answer

A)  20 km 
B)  22 km 
C)  25 km 
D)  27 km 
E)  30 km 
A)  20 km 
B)  22 km 
C)  25 km 
D)  27 km 
E)  30 km

Question 10

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 11

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)  0.93 Hz 
B)  0.00026 Hz 
C)  1.1 Hz 
D)  6.8 Hz 
E)  0.15 Hz 
A)  0.93 Hz 
B)  0.00026 Hz 
C)  1.1 Hz 
D)  6.8 Hz 
E)  0.15 Hz

Question 12

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 13

The intensity at a distance of 6.0 m from a source that is radiating equally in all directions is 6.0 × 10-10 W/m2. What is the intensity level in dB? The threshold of human hearing is 1.0 × 10-12 W/m2.

Accepted Answer

A)  18 dB 
B)  23 dB 
C)  28 dB 
D)  32 dB 
A)  18 dB 
B)  23 dB 
C)  28 dB 
D)  32 dB

Question 14

A rope with a total mass of 25.0 kg is tied to a tree on one side of a 125-m wide ravine. You are pulling on the other end of the rope with a force of 415 N. If you pluck the rope at your end, how long will it take the pulse to travel across the ravine to the tree?

Accepted Answer

The answer of A rope with a total mass of...

Question 15

What is the frequency of the wave shown in the figure?

Accepted Answer

A)  0.5 Hz. 
B)  1 Hz. 
C)  2 Hz. 
D)  4 Hz. 
E)  It cannot be determined from the given information. 
A)  0.5 Hz. 
B)  1 Hz. 
C)  2 Hz. 
D)  4 Hz. 
E)  It cannot be determined from the given information.

Question 16

A sound of 40 decibels is

Accepted Answer

A)  twice as intense as a sound of 20 decibels. 
B)  four times as intense as a sound of 20 decibels. 
C)  10 times as intense as a sound of 20 decibels. 
D)  100 times as intense as a sound of 20 decibels. 
E)  1000 times as intense as a sound of 20 decibels. 
A)  twice as intense as a sound of 20 decibels. 
B)  four times as intense as a sound of 20 decibels. 
C)  10 times as intense as a sound of 20 decibels. 
D)  100 times as intense as a sound of 20 decibels. 
E)  1000 times as intense as a sound of 20 decibels.

Question 17

You drop a stone down a well that is 9.5 m deep. How long is it before you hear the splash? The speed of sound in air is 343 m/s and air resistance is negligible.

Accepted Answer

A)  1.2 s 
B)  1.3 s 
C)  1.4 s 
D)  1.5 s 
E)  1.6 s 
A)  1.2 s 
B)  1.3 s 
C)  1.4 s 
D)  1.5 s 
E)  1.6 s

Question 18

A string of length L is under tension, and the speed of a wave in the string is v. What will be the speed of a wave in the string if the length is increased to 2L but with no change in the mass or tension?

Accepted Answer

A)  v/2 
B)  v/ $\sqrt { 2 }$ 
C)  v $\sqrt { 2 }$ 
D)  2v 
E)  4v 
A)  v/2 
B)  v/ $\sqrt { 2 }$ 
C)  v $\sqrt { 2 }$ 
D)  2v 
E)  4v

Question 19

If a wave has a speed of 362 m/s and a period of 4.17 ms, what is its wavelength?

Accepted Answer

A)  1510 m 
B)  1.51 m 
C)  86.8 m 
D)  86,800 m 
E)  0.0115 m 
A)  1510 m 
B)  1.51 m 
C)  86.8 m 
D)  86,800 m 
E)  0.0115 m

Question 20

What is the wavelength of the wave shown in the figure?

Accepted Answer

A)  8 m. 
B)  4 m. 
C)  2 m. 
D)  1 m. 
E)  It cannot be determined from the given information. 
A)  8 m. 
B)  4 m. 
C)  2 m. 
D)  1 m. 
E)  It cannot be determined from the given information.

Exam 15: Traveling Waves and Sound

An elephant can hear sound with a frequency of 15 Hz. What is the wavelength of this wave if the speed of sound in air is 343 m/s?

Find the speed of an ocean wave whose displacement is given by the equation y=3.7cos⁡(2.2x−5.6t)y = 3.7 \cos ( 2.2 x - 5.6 t )y=3.7cos(2.2x−5.6t) where x and y are in meters and t is in seconds.

A string of mass m is under tension, and the speed of a wave in the string is v. What will be the speed of a wave in the string if the mass of the string is increased to 2m but with no change in the length or tension?

A 15-m rope is pulled taut with a tension of 140 N. It takes 0.545 s for a wave to propagate along the rope. What is the mass of the rope?

A certain factory whistle can be heard up to a distance of 2.5 km. Assuming that the acoustic output of the whistle is uniform in all directions, how much acoustic power is emitted by the whistle? The threshold of human hearing is 1.0 × 10-12 W/m2.

Why does the intensity of waves from a small source decrease with the square of the distance from the source?

What is the intensity of a 70-dB sound? The threshold of human hearing is 1.0 × 10-12 W/m2.

The speed of sound through the ground is about 6.0 km/s while the speed of sound in air is 343 m/s. A very powerful explosion occurs some distance away and you feel the ground vibrate 60 seconds before you hear the sound of the explosion. How far away is the explosion?

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?

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

The intensity at a distance of 6.0 m from a source that is radiating equally in all directions is 6.0 × 10-10 W/m2. What is the intensity level in dB? The threshold of human hearing is 1.0 × 10-12 W/m2.

A rope with a total mass of 25.0 kg is tied to a tree on one side of a 125-m wide ravine. You are pulling on the other end of the rope with a force of 415 N. If you pluck the rope at your end, how long will it take the pulse to travel across the ravine to the tree?

What is the frequency of the wave shown in the figure?

A sound of 40 decibels is

You drop a stone down a well that is 9.5 m deep. How long is it before you hear the splash? The speed of sound in air is 343 m/s and air resistance is negligible.

A string of length L is under tension, and the speed of a wave in the string is v. What will be the speed of a wave in the string if the length is increased to 2L but with no change in the mass or tension?

If a wave has a speed of 362 m/s and a period of 4.17 ms, what is its wavelength?

What is the wavelength of the wave shown in the figure?

Representing Motion

Motion in One Dimension

Vectors and Motion in Two Dimensions

Forces and Newtons Laws of Motion

Applying Newtons Laws

Gravity

Rotational Motion

Equilibrium Ad Elasticity

Momentum

Energy and Work

Using Energy

Thermal Properties of Matter

Fluids

Oscillations

Superposition and Standing Waves

Wave Optics

Ray Optics

Optical Instruments

Electric Fields and Forces

Electric Potential

Current and Resistance

Circuits

Magnetic Fields and Forces

EM Induction and Em Waves

AC Electricity

Relativity

Quantum Physics

Atoms and Molecules

Nuclear Physics

Filters

Find the speed of an ocean wave whose displacement is given by the equation $y = 3.7 \cos ( 2.2 x - 5.6 t )$ where x and y are in meters and t is in seconds.

A certain factory whistle can be heard up to a distance of 2.5 km. Assuming that the acoustic output of the whistle is uniform in all directions, how much acoustic power is emitted by the whistle? The threshold of human hearing is 1.0 × 10^-12 W/m².

What is the intensity of a 70-dB sound? The threshold of human hearing is 1.0 × 10^-12 W/m².

The intensity at a distance of 6.0 m from a source that is radiating equally in all directions is 6.0 × 10^-10 W/m². What is the intensity level in dB? The threshold of human hearing is 1.0 × 10^-12 W/m².