Physics 011

A of PQ#12A

Chapter 12 : Sound
Practice Questions

1.	What are the units for Intensity? The correct answer: W/m^2 Review Section 12-2 in Giancoli.
2.	What are the units of Intensity Level? Your answer: dB
3.	What are the units of power?
4.	If 10^n=a then log10(a)=n, if e^n=a then loge(a)=n (e=2.17...). Use this to find the answer to this question. What is the log2(16)? The correct answer: 4 Review Appendix A-9 in Giancoli.
5.	If 10^n=a then log10(a)=n, if e^n=a then loge(a)=n (e=2.17...). Use this to find the answer to this question. What is the Log3(9)? Your answer: 2
6.	If 10^n=a then log10(a)=n, if e^n=a then loge(a)=n (e=2.17...). Use this to find the answer to this question. What is the Log4(2)? The correct answer: .5 Review Appendix A-9 in Giancoli.
7.	Log(2)+Log(3)= The correct answer: Log(6). Review Appendix A-9 in Giancoli.
8.	Log(2)-Log(3)= The correct answer: Log(2/3) Review Appendix A-9 in Giancoli.
9.	The Log(3^5)=
10.	What is the speed of sound if the temperature is 10 degrees Celsius? The correct answer: 337 m/s This is the speed of light. Review Section 12-1 in Giancoli.
11.	If the speed of sound is 350 m/s and the wavelength is 10 cm, what is the frequency? The correct answer: 3500 Hz. Review Example 12-7 in Giancoli.
12.	On a clear winter day the speed of sound at ground level is The correct answer: slower than the speed of sound in the upper air layer. The ground will be colder than the upper air. Review Section 12-1 in Giancoli.
13.	The intensity level of one sound is 5 dB above another one. The ratio of the intensity of the first to the second is The correct answer: 3.2/1 Review Example 12-3 in Giancoli.
14.	The intensity of one sound is 5 times the intensity of the second. What is the difference in the intensity level? The correct answer: 7 dB Review Example 12-3 in Giancoli.
15.	If you were to inhale a few breaths from a helium gas balloon, you would probably experience an amusing change in your voice. You would sound like Donald Duck or Alvin the Chipmunk. What is the cause of this curious high-pitched effect? The correct answer: Sound travels faster in helium than in air at a given temperature. Review Section 12-2 in Giancoli.
16.	A police car has an 1000 Hz siren. It is traveling at 35 m/s on a day when the speed of sound through air is 350 m/s. The car approaches and passes an observer who is standing along the roadside. What change of frequency does the observer hear? The correct answer: 202 Hz Review Section 12-8 in Giancoli.
17.	You are approaching a stationary sound of 1000 Hz at 35 m/s. What is the change in frequency of the sound as you pass? The correct answer: 200 Hz Review Section 12-8 in Giancoli.
18.	The wavelengths of the sounds produced by two horns are 6 m and 7 m respectively. What beat frequency is heard when the horns are sounded on a day when the velocity of sound is 336 m/s? The correct answer: 8 Review Section 12-7 in Giancoli.
19.	The wavelengths of the sounds produced by two horns are 6 m and 7 m respectively. By how much would the temperature have to change for the beat frequency to be 9 Hz? The correct answer: 70 C^o That would be true if the initial was 0 C^o. Review Section 12-7 in Giancoli.
20.	For a sound speed of 350 m/s, what would be the wavelength of a 5000 Hz sound? Your answer: 7 cm
21.	A sound speed of 350 m/s (5000 Hz) is played. Another sound is played along with this sound and a beat frequency of 5 Hz is heard. What is the frequency of the new sound?
22.	What is the frequency of the second harmonic of a 2 meter long stretched wire if the wave speed is 171.5 m/s? The correct answer: 85.75 This is the fourth harmonic. Review Section 12-5 in Giancoli.
23.	A 2 meter long stretched wire has a wave speed of 171.5 m/s. What is the wavelength of the sound produced by the vibrating wire if the temperature is 20 ^oC? The correct answer: 4 m You probably got the velocities backwards. Review Example 12-7 in Giancoli.
24.	What is the frequency of the first overtone of an open organ pipe .52 m long at an air temperature of 20 ^oC? Your answer: 660 Hz
25.	What is the frequency of the 2nd harmonic of a .52 m long closed organ pipe at a temperature of 20 ^oC? The correct answer: None of the above. The speed of sound is different than the wire speed. Review Example 12-7 in Giancoli.