# the velocity of the source is positive if the source is ______________. note that this equation may not use the sign convention you are accustomed to. think about the physical situation before answering.

### James

Guys, does anyone know the answer?

get the velocity of the source is positive if the source is ______________. note that this equation may not use the sign convention you are accustomed to. think about the physical situation before answering. from EN Bilgi.

## MasteringPhysics 2.0: Problem Print View

[ Problem View ] Doppler Shift

**Learning Goal:**To understand the terms in the Doppler shift formula.

The Doppler shift formula gives the frequency at which a listener L hears the sound emitted by a source S at frequency :

,

where is the speed of sound in the medium, is the velocity of the listener, and is the velocity of source.

Part A

The velocity of the source is positive if the source is ______________. Note that this equation may not use the sign convention you are accustomed to. Think about the physical situation before answering.

Hint A.1

ANSWER:

traveling in the + direction

traveling toward the listener

traveling away from the listener

Part B

The velocity of the source is measured with respect to the ________.

ANSWER:

medium (such as air or water)

listener Part C

The velocity of the listener is positive if the listener is _____________.

Hint C.1 **Relating the frequency and the listener's velocity**

ANSWER:

traveling in the + direction

traveling toward the source

traveling away from the source

Part D

The velocity of the listener is measured with respect to the ________.

ANSWER: source medium

Here are two rules to remember when using the Doppler shift formula:

Velocity is measured

The velocities are if they are in the direction from the

Part E

Imagine that the source is to the right of the listener, so that the positive reference direction (from the listener to the source) is in the direction. If the listener is stationary, what value does approach as the source's speed approaches the speed of sound moving to the right?

ANSWER: 0

It approaches infinity.

Part F

Now, imagine that the source is to the left of the listener, so that the positive reference direction is in the direction. If the source is stationary, what value does approach as the listener's speed (moving in the direction) approaches the speed of sound?

ANSWER: 0

It approaches infinity.

Basically in this case the listener doesn't hear anything since the sound waves cannot catch up with him or her.

Part G

In this last case, imagine that the listener is stationary and the source is moving toward the listener at the speed of sound. (Note that it is irrelevant whether the source is moving to the right or to the left.) What is when the sound waves reach the listener?

ANSWER: 0

It approaches infinity.

This case involves what is called a sonic boom. The listener will hear no sound () until the sonic boom reaches him or her (just as the source passes by). At that instant, the frequency will be infinite. There is no time between the passing waves--they are literally right on top of each other. That's a lot of energy to pass by the listener at once, which explains why a sonic boom is so loud.

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## Chapter 20 MC Flashcards

Start studying Chapter 20 MC. Learn vocabulary, terms, and more with flashcards, games, and other study tools.

## Chapter 20 MC

A telephone lineman is told to stretch the wire between two poles so the poles exert an 800N force on the wire. As the lineman does not have a scale to measure forces, he decides to measure the speed of a pulse created in the wire when he hits it with a wrench. The pulse travels 60m from one pole to the other and back again in 2.6s. The 60m wire has a mass of 15kg.

Click card to see definition 👆

tightened

Click again to see term 👆

Compare the intensity of a 100-W lightbulb while you are reading this book to the intensity of the Sun. Assume that the light bulb is a point source and that it is 1 m from your book. Compare the intensity of this lightbulb to the intensity of the Sun. Ignore atmospheric effects.

Click card to see definition 👆

The intensity of the lightbulb is about a hundred times less than the intensity of the Sun hitting the Earth.

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1/14 Created by michaela_howell2

### Terms in this set (14)

A telephone lineman is told to stretch the wire between two poles so the poles exert an 800N force on the wire. As the lineman does not have a scale to measure forces, he decides to measure the speed of a pulse created in the wire when he hits it with a wrench. The pulse travels 60m from one pole to the other and back again in 2.6s. The 60m wire has a mass of 15kg.

tightened

Compare the intensity of a 100-W lightbulb while you are reading this book to the intensity of the Sun. Assume that the light bulb is a point source and that it is 1 m from your book. Compare the intensity of this lightbulb to the intensity of the Sun. Ignore atmospheric effects.

The intensity of the lightbulb is about a hundred times less than the intensity of the Sun hitting the Earth.

y=(0.2m)sin[π2(t+x20m/s)]

Say everything you can about this wave.

The wave has an amplitude of 0.2m.

The frequency of the wave is f=0.25Hz

The magnitude of its velocity is 20m/s.

Its wavelength is λ=80m.

Since the sign is positive in the argument of the sine function, the wave travels in the negative x direction.

Its period is T=4s.

Four waves are described by the following equations, 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 have the same speed?

1 and 2

Estimate the fundamental frequency of vibration of a telephone line between adjacent poles. Assume the distance between poles is 50 m and tension ot the wire is 200 N. Typical telephone wire in the US has a cross section of 0.33 mm2. Density of copper is 8.90 g/cm3.

f = 2.6 Hz

The lowest three standing wave vibration frequencies of an organ pipe are 120 Hz, 360 Hz, and 600 Hz. Is the pipe open or closed?

the pipe is closed

The lowest three standing wave vibration frequencies of an organ pipe are 120 Hz, 360 Hz, and 600 Hz. What is the pipe's length?

L = 0.71 m

The velocity of the source is positive if the source is ______________. Note that this equation may not use the sign convention you are accustomed to. Think about the physical situation before answering.

traveling away from the listener

The velocity of the source is measured with respect to the _________.

medium (such as air or water)

The velocity of the listener is positive if the listener is ____________.

traveling toward the source

The velocity of the listener is measured with respect to the _________.

medium

Imagine that the source is to the right of the listener, so that the positive reference direction (from the listener to the source) is in the +x direction. If the listener is stationary, what value does fL approach as the source's speed approaches the speed of sound moving to the right?

1/2(fs)

Now, imagine that the source is to the left of the listener, so that the positive reference direction is in the −x direction. If the source is stationary, what value does fL approach as the listener's speed (moving in the +x direction) approaches the speed of sound?

0

In this last case, imagine that the listener is stationary and the source is moving toward the listener at the speed of sound. (Note that it is irrelevant whether the source is moving to the right or to the left.) What is fL when the sound waves reach the listener?

It approaches infinity.

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## mastering physics

The Dppler Effect Due: 3:00pm on Monday, October 24, 2011 Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy…

## mastering physics

Download Report View 10.351 Download 27 Embed Size (px) DESCRIPTION dopler effect

### Text of mastering physics

The Dppler EffectDue: 3:00pm on Monday, October 24, 2011 Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy [Switch to Standard Assignment View]

Doppler ShiftLearning Goal: To understand the terms in the Doppler shift formula. The Doppler shift formula gives the frequency by a source S at frequency : at which a listener L hears the sound emitted

, where is the speed of sound in the medium, velocity of source. Part A is the velocity of the listener, and is the

The velocity of the source is positive if the source is ______________. Note that this equation may not use the sign convention you are accustomed to. Think about the physical situation before answering. Hint A.1 Relating the frequency and the source velocity Hint not displayed ANSWER: traveling in the +x direction traveling toward the listener traveling away from the listener Correct Part B The velocity of the source is measured with respect to the ________. ANSWER: medium (such as air or water) listener Correct

Part C The velocity of the listener is positive if the listener is _____________. Hint C.1 Relating the frequency and the listener's velocity Hint not displayed ANSWER: traveling in the +x direction traveling toward the source traveling away from the source Correct Part D The velocity of the listener is measured with respect to the ________. ANSWER: source medium Correct Here are two rules to remember when using the Doppler shift formula: 1. Velocity is measured with respect to the medium. 2. The velocities are positive if they are in the direction from the listener to the source. Part E Imagine that the source is to the right of the listener, so that the positive reference direction (from the listener to the source) is in the direction. If the listener is stationary, what value does approach as the source's speed approaches the speed of sound moving to the right? ANSWER: 0

It approaches infinity.

Correct

Part F Now, imagine that the source is to the left of the listener, so that the positive reference direction is in the direction. If the source is stationary, what value does approach as the listener's speed (moving in the ANSWER: 0 direction) approaches the speed of sound?

It approaches infinity.

Correct Basically in this case the listener doesn't hear anything since the sound waves cannot catch up with him or her. Part G In this last case, imagine that the listener is stationary and the source is moving toward the listener at the speed of sound. (Note that it is irrelevant whether the source is moving to the right or to the left.) What is ANSWER: 0 when the sound waves reach the listener?

It approaches infinity.

Correct This case involves what is called a sonic boom. The listener will hear no sound ( ) until the sonic boom reaches him or her (just as the source passes by). At that instant, the frequency will be infinite. There is no time between the passing waves--they are literally right on top of each other. That's a lot of energy to pass by the listener at once, which explains why a sonic boom is so loud.

Two Traveling Waves Beating TogetherLearning Goal: To see how two traveling waves of nearly the same frequency can create

beats and to interpret the superposition as a "walking" wave. Consider two similar traveling transverse waves, which might be traveling along a string for example: and They are similar because we assume that nearly equal. Part A and . are nearly equal and also that and are

Which one of the following statements about these waves is correct? ANSWER: Both waves are traveling in the direction. Both waves are traveling in the Only wave Only wave Correct The principle of superposition states that if two waves each separately satisfy the wave equation then the sum (or difference) also satisfies the wave equation. This follows from the fact that every term in the wave equation is linear in the amplitude of the wave. Consider the sum of the two waves given in the introduction, that is, . These waves have been chosen so that their sum can be written as follows: is traveling in the is traveling in the direction. direction. direction.

where

is a constant, and the functions

and

are trigonometric functions of and

. This form is especially significant because the first function, called the envelope, is a slowly varying function of both position ( ) and time ( ), whereas the second varies rapidly with both position ( ) and time ( ). Traditionally, the overall amplitude is represented by the constant and are trigonometric functions with unit amplitude. Part B Find , , and . Hint B.1 A useful trigonometric identity Hint not displayed Hint B.2 Which is the envelope and which is the carrier wave? Hint not displayed Express your answer in terms of , , , , , , and . Separate the three terms with commas. Recall that (the second term) varies slowly whereas (the third term) varies quickly. Both and should be trigonometric functions of unit amplitude. ANSWER: , , , = All attempts used; correct answer displayed Part C Which of the following statements about is correct? ANSWER: It is a rapidly oscillating wave traveling in the It is a rapidly oscillating wave traveling in the , , while the functions

Guys, does anyone know the answer?