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Physics

Problems

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Problems

14.1 Speed of Sound, Frequency, and Wavelength

25 .
A bat produces a sound at 17 , 250 Hz and wavelength 0.019 m . What is the speed of the sound?
  1. 1.7 × 10 6 m / s
  2. 8.6 × 10 5 m / s
  3. 1.15 × 10 − 6 m/s
  4. 3.28 × 10 2 m / s
26 .
Medium vw (m/s)
Gases at 0 °C
Air 331
Carbon dioxide 259
Oxygen 316
Helium 965
Hydrogen 1290
Liquids at 20 °C
Ethanol 1160
Mercury 1450
Water, fresh 1480
Sea water 1540
Human tissue 1540
Solids (longitudinal or bulk)
Vulcanized rubber 54
Polyethylene 920
Marble 3810
Glass, Pyrex 5640
Lead 1960
Aluminum 5120
Steel 5960
Table 14.2
A sound wave with a frequency of 80 Hz is traveling through air at 0°C. The sound wave enters a block of aluminum. If the sound's frequency does not change, what happens to the sound's wavelength?
  1. It's wavelength increases by a factor of 4.2.
  2. It's wavelength increases by a factor of 18.
  3. It's wavelength decreases by a factor of 4.2.
  4. It's wavelength decreases by a factor of 18.

14.2 Sound Intensity and Sound Level

27.

Calculate the sound intensity for a sound wave traveling through air at 15° C and having a pressure amplitude of 0.80 Pa. (Hint—Speed of sound in air at 15° C is 340 m/s .)

  1. 9.6×10−3 W / m2
  2. 7.7×10−3 W / m2
  3. 9.6×10−4 W / m2
  4. 7.7×10−4 W / m2
28 .
The sound level in dB of a sound traveling through air at 0 ∘ C is 97 dB . Calculate its pressure amplitude.
  1. 4.3 Pa
  2. 0.20 Pa
  3. 0.04 Pa
  4. 2.1 Pa

14.3 Doppler Effect and Sonic Booms

29 .
(credit: modification of work by Insights Active Learning)
An ambulance is moving away from you. You are standing still and you hear its siren at a frequency of 101 Hz. You know that the actual frequency of the siren is 105 Hz. Assuming the speed of sound is 331 m/s, what is the speed of the ambulance?
  1. 17.07 m / s
  2. 16.55 m / s
  3. 14.59 m / s
  4. 13.1 m/s
30 .
(credit: modification of work by Radiology Key)
An ambulance passes you at a speed of 15.0m/s and its siren has a frequency of 995 Hz. Assuming the speed of sound in air is 331m/s, what is difference in the frequencies you perceive before and after it passes you?
  1. 47.0 Hz
  2. 43.0 Hz
  3. 94.9 Hz
  4. 90.0 Hz

14.4 Sound Interference and Resonance

31 .
What is the length of an open-pipe resonator with a fundamental frequency of 400.0 Hz ? (Assume the speed of sound is 331 m/s .)
  1. 165.1 cm
  2. 82.22 cm
  3. 20.25 cm
  4. 41.38 cm
32 .
An open-pipe resonator has a fundamental frequency of 250 Hz . By how much would its length have to be changed to get a fundamental frequency of 300.0 Hz ? (Assume the speed of sound is 331 m/s .)
  1. 77.32 cm
  2. 44.09 cm
  3. 32.16 cm
  4. 11.03 cm
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