SHM, Waves, Thermo, E&M Practice Problem Workbook
SHM, Waves, Thermo, E&M Practice Problem Workbook
SHM, Waves, Thermo, E&M Practice Problem Workbook
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MECHANICS PRACTICE PROBLEM SETS 4<br />
7.2 SOUND<br />
Unless stated otherwise, assume that T = 20°C.<br />
1. Find the frequency of a sound wave moving in air at a temperature of 22°C with a<br />
wavelength of 0.667 m.<br />
Answer: f = 516 Hz<br />
2. You hear the sound of the firing of a distant cannon 6.0 seconds after seeing the flash.<br />
How far are you from the cannon<br />
Answer: d = 2.1 km<br />
3. A sound wave with a frequency of 9800 Hz travels along a copper pipe. If the<br />
wavelength is 0.370 m and the density of copper is 8.9 x 10 3 kg/m 3 , what is the elastic<br />
modulus of copper Answer: E= 1.2 x 10 11 N/m 2<br />
4. A certain instant camera determines the distance to the subject by sending out a sound<br />
wave and measuring the time needed for the echo to return to the camera. How long<br />
will it take the sound wave to return to the camera if the subject were 3.00 m away<br />
Answer: t = 0.017 s<br />
5. If you drop a stone into a mineshaft that is 122.5 m deep, how soon after you drop the<br />
stone do you hear it hit the bottom of the shaft The temperature in the mineshaft is<br />
10°C.<br />
Answer: t = 5.36 s<br />
6. With what tension must a rope of length 2.50 m and mass of 0.120 kg be stretched for<br />
transverse waves of frequency of 40.0 Hz to have a wavelength of 0.750 m<br />
Answer: T= 43.2 N<br />
7. A ship uses a sonar system to detect underwater objects in the ocean. The system<br />
emits underwater sound waves and measures the time interval for the reflected wave<br />
to return to the detector.<br />
a. Determine the speed of sound in seawater if the bulk modulus is 2.2 x 10 9<br />
N/m 2 .<br />
Answer: v= 1465 m/s<br />
b. The ship is on the continental shelf when it emits a sound wave. It takes the<br />
echo 0.203 seconds to be picked up by the detector. What is the depth of the<br />
ocean on the continental shelf Answer: depth = 150 m.<br />
8. A tuning fork of frequency 262 Hz is sounded at the same time as another tuning fork<br />
with a frequency of 257 Hz. What is the beat frequency that is heard<br />
Answer: f b = 5 Hz<br />
9. A tuning fork with a frequency of 432 Hz is sounded at the same time as a guitar. If 6<br />
beats are heard in 3 seconds, what are the possible frequencies of the guitar string<br />
Answer: f = 430 Hz or 434 Hz<br />
Gamzon & Gregorian-Michaelsen 6/13/12
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