# Quiz6a - Exam Phys 2C, Fall 11 Name_Mechanical waves_...

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Exam Phys 2C, Fall 11 Name__Mechanical waves_________________________________ MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A 660 - Hz tone has an intensity level of 54 dB. The velocity of sound in air is 345 m/s. The bulk modulus of air is 142 kPa. The pressure amplitude of the sound waves, in SI units, is closest to: A) 2.9 × 10 - 3 B) 7.2 × 10 - 3 C) 1.4 × 10 - 3 D) 1.4 × 10 - 2 E) 2.9 × 10 - 2 2) Which of the following is a WRONG statement? A) The wavelength of a light wave measured by an observer moving with respect to the source is different from the wavelength measured by an observer at rest with respect to the source. B) The speed of sound waves emitted by a moving source is the same as by the source at rest. C) The frequency of a sound wave measured by an observer moving with respect to the source is different from the frequency measured by an observer at rest with respect to the source. D) The Doppler shift in the frequency and wavelength of an electromagnetic wave depends only on the relative velocity of the observer with respect to the source and does not depend on motion of the source with respect to the medium. E) The Doppler shift in the wavelength of a sound wave in the atmosphere depends on the position and velocity of the observer with respect to the source. 3) A car on a road parallel to and right next to a railroad track is approaching a train. The car is traveling eastward at 30.0 m/s while the train is going westward at 50.0 m/s. There is no wind, and the speed of sound is 344 m/s. The car honks its horn at a frequency of 1.00 kHz as the train toots its whistle at a frequency of 1.50 kHz. The frequency that the car's driver hears from the train's whistle is closest to: A) 1.18 kHz B) 1.91 kHz C) 1.95 kHz D) 1.15 kHz E) 1.20 kHz 4) At a distance of 2.00 m from a point source of sound, the intensity level is 80.0 dB. At a distance of 4.00 m from this source, the intensity level will be closest to: A) 77.0 dB B) 74.0 dB C) 40.0 dB D) 20.0 dB E) 60.0 dB 5) Sound takes 10.0 ms to travel across a certain experimental enclosure. If the absolute temperature in this enclosure is doubled, the time for sound to travel across it will be closest to: A) 7.07 ms B) 20.0 ms C) 5.00 ms D) 14.1 ms E) 2.50 ms 6) Which of the following is a WRONG statement A) Bulk modulus of elasticity of an ideal gas is equal to the product of the pressure and adiabatic constant of the gas. B) A standing wave on a string can be represented as a result of interference of two waves with equal amplitudes and frequencies propagating in opposite directions. C) Longer waves on the surface of deep water propagate faster than shorter waves. D) For a string with a length

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## This note was uploaded on 11/26/2011 for the course PHYSICS 2C taught by Professor Hicks during the Spring '09 term at UCSD.

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Quiz6a - Exam Phys 2C, Fall 11 Name_Mechanical waves_...

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