Chapter 2: Waves/Acoustics

Expert-verified

Pages: 467 - 543

Book edition 14th edition

Author(s) Hugh D. Young, Roger A. Freedman

Pages 1596 pages

ISBN 9780321973610

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173 Questions for Chapter 2: Waves/Acoustics

A sinusoidal wave can be described by a cosine function, which is negative just as often as positive. So why isn’t the average power delivered by this wave zero?

Found on Page 496
Question: Energy Delivered to the Ear. Sound is detected when a sound wave causes the tympanic membrane (the eardrum) to vibrate. Typically, the diameter of this membrane is about 8.4 mm in humans. (a) How much energy is delivered to the eardrum each second when someone whispers (20 dB) a secret in your ear? (b) To comprehend how sensitive the ear is to very small amounts of energy, calculate how fast a typical 2.0-mg mosquito would have to fly (in mm/s) to have this amount of kinetic energy.

Found on Page 539
Two strings of different mass per unit length μ1and μ2are tied together and stretched with a tension F. A wave travels along the string and passes the discontinuity in μ. Which of the following wave properties will be the same on both sides of the discontinuity, and which will change: speed of the wave; frequency; wavelength? Explain the physical reasoning behind each answer.

Found on Page 496
A sinusoidal wave is propagating along a stretched string that lies along the x-axis. The displacement of the string as a function of time is graphed in Fig. E15.11 for particles at \({\bf{x}}{\rm{ }} = {\rm{ }}{\bf{0}}\) and at\(x = 0.0900 m\). (a) What is the amplitude of the wave? (b) What is the period of the wave? (c) You are told that the two points \({\bf{x}}{\rm{ }} = {\rm{ }}{\bf{0}}\) and \(x = 0.0900 m\) are within one wavelength of each other. If the wave is moving in the +x direction, determine the wavelength and the wave speed. (d) If instead the wave is moving in the –x direction, determine the wavelength and the wave speed. (e) Would it be possible to determine definitively the wavelengths in parts (c) and (d) if you were not told that the two points were within one wavelength of each other? Why or why not?

Found on Page 467
Question:A 60.0-m-long brass rod is struck at one end. A person at the other end hears two sounds as a result of two longitudinal waves, one traveling in the metal rod and the other traveling in air. What is the time interval between the two sounds? (The speed of sound in air is 344 m/s; see Tables 11.1 and 12.1 for relevant information about brass.)

Found on Page 539
A long rope with mass m is suspended from the ceiling and hangs vertically. A wave pulse is produced at the lower end of the rope, and the pulse travels up the rope. Does the speed of the wave pulse change as it moves up the rope, and if so, does it increase or decrease? Explain.

Found on Page 496
Question:What must be the stress (F/A) in a stretched wire of a material whose Young’s modulus is Yfor the speed of longitudinal waves to equal 30 times the speed of transverse waves?

Found on Page 539
Speed of Propagation vs. Particle Speed. (a) Show that Eq. (15.3) may be written as

Found on Page 498
In a transverse wave on a string, the motion of the string is perpendicular to the length of the string. How, then, is it possible for energy to move along the length of the string?

Found on Page 496
Question: (a) By what factor must the sound intensity be increased to raise the sound intensity level by 13.0 dB? (b) Explain why you don’t need to know the original sound intensity.

Found on Page 539

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Chapter 2: Waves/Acoustics

University Physics with Modern Physics

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173 Questions for Chapter 2: Waves/Acoustics

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