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Chapter 16: Q. 39 (page 452)
A loudspeaker on a tall pole broadcasts sound waves equally in all directions. What is the speaker鈥檚 power output if the sound intensity level is 90 dB at a distance of 20 m?
The power output of the speaker is.
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The G string on a guitar is a 0.46-mm-diameter steel string
with a linear density of 1.3 g/m. When the string is properly
tuned to 196 Hz, the wave speed on the string is 250 m/s. Tuning
is done by turning the tuning screw, which slowly tightens鈥攁nd
stretches鈥攖he string. By how many mm does a 75-cm-long G
string stretch when it鈥檚 first tuned?
You have just been pulled over for running a red light, and
the police officer has informed you that the fine will be \(250. In
desperation, you suddenly recall an idea that your physics professor recently discussed in class. In your calmest voice, you tell the officer that the laws of physics prevented you from knowing that the light was red. In fact, as you drove toward it, the light was Doppler shifted to where it appeared green to you. 鈥淥K,鈥� says the officer, 鈥淭hen I鈥檒l ticket you for speeding. The fine is \)1 for every 1 km/h over the posted speed limit of 50 km/h.< How big is your fine? Use 650 nm as the wavelength of red light and 540 nm as the wavelength of green light.
A friend of yours is loudly singing a single note at 400 Hz while racing toward you at 25.0 m/s on a day when the speed of sound is 340 m/s. a. What frequency do you hear? b. What frequency does your friend hear if you suddenly start singing at 400 Hz?
A circular wave travels outward from the origin. At one instant of time, the phase at r1 = 20 cm is 0 rad and the phase at r2 = 80 cm is 3p rad. What is the wavelength of the wave?
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