Physics 011

Chapter 12: Sound
Practice Questions

Quiz#12

 1 What are the units for Intensity? J J/m2 W/m2 decibels 2 What are the units of Intensity Level? J J/m2 W/m2 dB 3 What are the units of power? W/s J/s decibel/s J/m2s 4 If 10n=a then log10(a)=n, if en=a then loge(a)=n (e=2.17...). Use this to find the answer to this question. What is the log2(16)? 2 4 8 16 5 If 10n=a then log10(a)=n, if en=a then loge(a)=n (e=2.17...). Use this to find the answer to this question. What is the Log3(9)? 2 3 4 5 6 If 10n=a then log10(a)=n, if en=a then loge(a)=n (e=2.17...). Use this to find the answer to this question. What is the Log4(2)? .5 1 1.5 2 7 Log(2)+Log(3)= Log(2/3). Log(6). Log(3/2). Log(5). 8 Log(2)-Log(3)= Log(2/3) Log(6) Log(3/2) Log(1) 9 The Log(35)= Log(15). 3Log(5) 5Log(3) None of the above. 10 What is the speed of sound if the temperature is 10 degrees Celsius? 331 m/s 337 m/s 343 m/s 3x108 m/s 11 If the speed of sound is 350 m/s and the wavelength is 10 cm, what is the frequency? 35 Hz. 1750 Hz. 3500 Hz. 35000 Hz. 12 On a clear winter day the speed of sound at ground level is faster than the speed of sound in the upper air layer. slower than the speed of sound in the upper air layer. the same as speed of sound in the upper air layer. 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 1.6/1 3.2/1 5/1 10/1 14 The intensity of one sound is 5 times the intensity of the second. What is the difference in the intensity level? .7 dB 5 dB 7 dB 10 dB 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 helium causes your vocal cords to tighten and vibrate at a higher frequency. For a given frequency of vibration of your vocal cords, the wavelength of sound is less in helium than it is in air. Your voice box is resonating at the second harmonic, rather than at the fundamental frequency. Low frequencies are absorbed in helium gas, leaving the high frequency components which result in the high, squeaky sound. Sound travels faster in helium than in air at a given temperature. 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? 81 Hz 111 Hz 202 Hz 1111 Hz 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? 100 Hz 90 Hz 110 Hz 200 Hz 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? 53.5 8 4 None of the above. 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? 78 Co 70 Co 25 Co The beat frequency is independent of the temperature. 20 For a sound speed of 350 m/s, what would be the wavelength of a 5000 Hz sound? 2 cm 3.5 cm 5 cm 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? 4998 Hz or 5003 Hz 4997 Hz or 5002 Hz 4995 Hz or 5000 Hz 5000 Hz or 5005 Hz 4995 Hz or 5005 Hz 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? 42.88 85.75 128.63 171.5 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? 1 m 2 m 4 m 8 m 24 What is the frequency of the first overtone of an open organ pipe .52 m long at an air temperature of 20 oC? 660 Hz 330 Hz 990 Hz None of the above. 25 What is the frequency of the 2nd harmonic of a .52 m long closed organ pipe at a temperature of 20 oC? 330 Hz 660 Hz 990Hz None of the above.