Physics
Physics
1st Edition
Walker
ISBN: 9780133256925
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Textbook solutions

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Page 519: Lesson Check

Exercise 53
Step 1
1 of 2
The sound is distributed over a larger area as it travels away from the source. Consequently, the intensity is reduced (Intensity is inversely proportional as area). Similarly, as you go closer from the source, more power is subjected to a smaller area. In effect, the sound gets larger.
Result
2 of 2
Click here to see the explanation
Exercise 54
Step 1
1 of 2
To compare the loudness ratio an observer will experience when subject to two different alarm clocks, one of which is $20text{ dB}$ louder than the other, we will first remember that:

Our perception of sound is such that doubling the loudness corresponds to increasing the intensity by a factor of 10, which corresponds to an increase of $10text{ dB}$.

Keeping that in mind, a difference of $20text{ dB}$ will produce a doubling effect of the loudness twice. This means that the louder alarm will seem 4 times louder.

Result
2 of 2
The louder alarm will seem 4 times louder.
Exercise 55
Step 1
1 of 2
The intensity of sound coming a from a point source is defined as the power produced divided by its area $4pi r^2$. Since it varies inversely as the square of the distance from the source, the sound intensity decreases by a factor of 4 if the distance is doubled.
Result
2 of 2
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Exercise 56
Step 1
1 of 2
When a sound travels, a pressure difference occurs in the areas of compression (high pressure) and rarefaction (low pressure). A pressure does exert force on an object making it capable of doing work, as well as energy transfer. Therefore, regions of compression and rarefaction in sound waves do transfer energy from one place to another.
Result
2 of 2
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Exercise 57
Step 1
1 of 3
### Theoretical reminder

The amount of energy carried by a sound wave through a given area in a given time is the intensity $I$. It can be calculated via power $P$ and area $A$ as follows:

$$
begin{equation}
I = frac{P}{A}
end{equation}
$$

Step 2
2 of 3
### Calculation

We know that the intensity of the sound wave is $I = 4.4 cdot 10^{-4} ; frac{text{W}}{text{m}^2}$. And the area through which it passes is $A = 1.8text{ m}^2$

Finding the power of the sound source is done simply, using formula (1) as follows:

$$
begin{align*}
I = frac{P}{A}
end{align*}
$$

Rearranging for $P$ :

$$
begin{align*}
P = I cdot A
end{align*}
$$

Plugging in the values we get:

$$
begin{align*}
P = 4.4 cdot 10^{-4} ; frac{text{W}}{text{m}^2} cdot 1.8text{ m}^2 approx 7.9 cdot 10^{-4}text{ W}
end{align*}
$$

Result
3 of 3
The power of the sound source is $P = 7.9 cdot 10^{-4}text{ W}$
Exercise 58
Step 1
1 of 3
### Theoretical reminder

The amount of energy carried by a sound wave through a given area in a given time is the intensity $I$. It can be calculated via power $P$ and area $A$ as follows:

$$
begin{align*}
I = frac{P}{A}
end{align*}
$$

For spherical wave expansion the area becomes:

$$
begin{align*}
A = 4 , r^2 , pi
end{align*}
$$

So we get finally:

$$
begin{equation}
I = frac{P}{4 , r^2 , pi}
end{equation}
$$

Where $r$ is the distance from the sound source to the wave front.

Step 2
2 of 3
### Calculation

We know the power of the sound source is $P = 25text{ W}$, and the distance from the point to the source is $r = 5.1text{ m}$.

Now using formula (1) we find the intensity as follows:

$$
begin{align*}
I = frac{P}{4 , r^2 , pi}
end{align*}
$$

Plugging in the values we get:

$$
begin{align*}
I = frac{25text{ W}}{4 , (5.1text{ m})^2 , pi} approx 0.077 ; frac{text{W}}{text{m}^2}
end{align*}
$$

Result
3 of 3
The intensity is $I = 0.077 ; frac{text{W}}{text{m}^2}$
Exercise 59
Step 1
1 of 2
The concept is that an increase of 10 dB intensity level requires a 10 times increase in sound intensity. Therefore, to increase the intensity by 10 dB, you need 10 car horns sounding simultaneously.
Result
2 of 2
10 car horns
Exercise 60
Step 1
1 of 2
The concept is that an increase of 10 dB intensity level requires a 10 times increase in sound intensity. So, 20 dB corresponds to 100 increase in sound power.

100 violins will have 100 times the power of 1 violin.

Therefore, a single violin produced 20 dB quitter than 100 violins.

The difference in intensity level is

$$
difference=76 ;dB-20;dB=56;dB
$$

Result
2 of 2
56 dB
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Chapter 1: Introduction to Physics
Section 1.1: Physics and the Scientific Method
Section 1.2: Physics and Society
Section 1.3: Units and Dimensions
Section 1.4: Basic Math for Physics
Page 38: Assessment
Page 41: Standardized Test Prep
Chapter 2: Introduction to Motion
Section 2.1: Describing Motion
Section 2.2: Speed and Velocity
Section 2.3: Position-Time Graphs
Section 2.4: Equation of Motion
Page 66: Assessment
Page 71: Standardized Test Prep
Page 45: Practice Problems
Page 47: Practice Problems
Page 47: Lesson Check
Page 49: Practice Problems
Page 52: Practice Problems
Page 53: Lesson Check
Page 56: Practice Problems
Page 57: Lesson Check
Page 59: Practice Problems
Page 60: Practice Problems
Page 62: Practice Problems
Page 62: Lesson Check
Chapter 3: Acceleration and Acceleration Motion
Section 3.1: Acceleration
Section 3.2: Motion with Constant Acceleration
Section 3.3: Position-Time Graphs for Constant Acceleration
Section 3.4: Free Fall
Page 105: Assessment
Page 111: Standardized Test Prep
Chapter 4: Motion in Two Dimensions
Section 4.1: Vectors in Physics
Section 4.2: Adding and Subtracting Vectors
Section 4.3: Relative Motion
Section 4.4: Projectile Motion
Page 144: Assessment
Page 149: Standardized Test Prep
Chapter 5: Newton’s Laws of Motion
Section 5.1: Newton’s Laws of Motion
Section 5.2: Applying Newton’s Laws
Section 5.3: Friction
Page 180: Assessment
Page 187: Standardized Test Prep
Chapter 6: Work and Energy
Section 6.1: Work
Section 6.2: Work and Energy
Section 6.3: Conservation of Energy
Section 6.4: Power
Page 220: Assessment
Page 227: Standardized Test Prep
Page 191: Practice Problems
Page 193: Practice Problems
Page 196: Lesson Check
Page 196: Practice Problems
Page 199: Practice Problems
Page 201: Practice Problems
Page 203: Practice Problems
Page 204: Practice Problems
Page 205: Practice Problems
Page 206: Lesson Check
Page 209: Practice Problems
Page 211: Lesson Check
Page 213: Practice Problems
Page 214: Practice Problems
Page 215: Practice Problems
Page 216: Lesson Check
Chapter 7: Linear Momentum and Collisions
Section 7.1: Momentum
Section 7.2: Impulse
Section 7.3: Conservation of Momentum
Section 7.4: Collisions
Page 260: Assessment
Page 265: Standardized Test Prep
Chapter 8: Rotational Motion and Equilibrium
Section 8.1: Describing Angular Motion
Section 8.2: Rolling Motion and the Moment of Inertia
Section 8.3: Torque
Section 8.4: Static Equilibrium
Page 300: Assessment
Page 305: Standardized Test Prep
Page 269: Practice Problems
Page 271: Practice Problems
Page 272: Practice Problems
Page 275: Practice Problems
Page 275: Lesson Check
Page 277: Practice Problems
Page 280: Lesson Check
Page 284: Practice Problems
Page 286: Practice Problems
Page 287: Practice Problems
Page 289: Lesson Check
Page 294: Practice Problems
Page 295: Practice Problems
Page 296: Lesson Check
Chapter 9: Gravity and Circular Motion
Section 9.1: Newton’s Law of Universal Gravity
Section 9.2: Applications of Gravity
Section 9.3: Circular Motion
Section 9.4: Planetary Motion and Orbits
Page 336: Assessment
Page 341: Standardized Test Prep
Chapter 10: Temperature and Heat
Section 10.1: Temperature, Energy, and Heat
Section 10.2: Thermal Expansion and Energy Transfer
Section 10.3: Heat Capacity
Section 10.4: Phase Changes and Latent Heat
Page 378: Assessment
Page 383: Standardized Test Prep
Chapter 11: Thermodynamics
Section 11.1: The First Law of Thermodynamics
Section 11.2: Thermal Processes
Section 11.3: The Second and Third Laws of Thermodynamics
Page 410: Assessment
Page 413: Standardized Test Prep
Chapter 12: Gases, Liquids, and Solids
Section 12.1: Gases
Section 12.2: Fluids at Rest
Section 12.3: Fluids in Motion
Section 12.4: Solids
Page 446: Assessment
Page 451: Standardized Test Prep
Chapter 13: Oscillations and Waves
Section 13.1: Oscillations and Periodic Motion
Section 13.2: The Pendulum
Section 13.3: Waves and Wave Properties
Section 13.4: Interacting Waves
Page 486: Assessment
Page 491: Standardized Test Prep
Chapter 14: Sound
Section 14.1: Sound Waves and Beats
Section 14.2: Standing Sound Waves
Section 14.3: The Doppler Effect
Section 14.4: Human Perception of Sound
Page 523: Assessment
Page 527: Standardized Test Prep
Page 495: Practice Problems
Page 496: Practice Problems
Page 500: Practice Problems
Page 501: Lesson Check
Page 503: Practice Problems
Page 504: Practice Problems
Page 506: Practice Problems
Page 506: Lesson Check
Page 510: Practice Problems
Page 511: Practice Problems
Page 512: Lesson Check
Page 514: Practice Problems
Page 516: Practice Problems
Page 517: Practice Problems
Page 519: Lesson Check
Chapter 15: The Properties of Lights
Section 15.1: The Nature of Light
Section 15.2: Color and the Electromagnetic Spectrum
Section 15.3: Polarization and Scattering of Light
Page 557: Assessment
Page 563: Standardized Test Prep
Chapter 16: Reflection and Mirrors
Section 16.1: The Reflection of Light
Section 16.2: Plane Mirrors
Section 16.3: Curved Mirrors
Page 590: Assessment
Page 595: Standardized Test Prep
Chapter 17: Refraction and Lenses
Section 17.1: Refraction
Section 17.2: Applications of Refraction
Section 17.3: Lenses
Section 17.4: Applications of Lenses
Page 629: Assessment
Page 635: Standardized Test Prep
Chapter 18: Interference and Diffraction
Section 18.1: Interference
Section 18.2: Interference in Thin Films
Section 18.3: Diffraction
Section 18.4: Diffraction Gratings
Page 668: Assessment
Page 673: Standardized Test Prep
Chapter 19: Electric Charges and Forces
Section 19.1: Electric Charge
Section 19.2: Electric Force
Section 19.3: Combining Electric Forces
Page 698: Assessment
Page 703: Standardized Test Prep
Chapter 20: Electric Fields and Electric Energy
Section 20.1: The Electric Field
Section 20.2: Electric Potential Energy and Electric Potential
Section 20.3: Capacitance and Energy Storage
Page 738: Assessment
Page 743: Standardized Test Prep
Chapter 21: Electric Current and Electric Circuits
Section 21.1: Electric Current, Resistance, and Semiconductors
Section 21.2: Electric Circuits
Section 21.3: Power and Energy in Electric Circuits
Page 775: Assessment
Page 781: Standardized Test Prep
Chapter 22: Magnetism and Magnetic Fields
Section 22.1: Magnets and Magnetic Fields
Section 22.2: Magnetism and Electric Currents
Section 22.3: The Magnetic Force
Page 810: Assessment
Page 815: Standardized Test Prep
Chapter 23: Electromagnetic Induction
Section 23.1: Electricity from Magnetism
Section 23.2: Electric Generators and Motors
Section 23.3: AC Circuits and Transformers
Page 844: Assessment
Page 849: Standardized Test Prep
Chapter 24: Quantum Physics
Section 24.1: Quantized Energy and Photons
Section 24.2: Wave-Particle Duality
Section 24.3: The Heisenberg Uncertainty Principle
Page 876: Assessment
Page 881: Standardized Test Prep
Chapter 26: Nuclear Physics
Section 26.1: The Nucleus
Section 26.2: Radioactivity
Section 26.3: Applications of Nuclear Physics
Section 26.4: Fundamental Forces and Elementary Particles
Page 944: Assessment
Page 947: Standardized Test Prep