Physics 011

MC#12A

Chapter 12: Sound

1.	At 0^oC, approximately how long does it take sound to travel 5.00 km? The correct answer: 15 s See Sections 12-1, 11-2
2.	In which medium will the speed of sound of frequency 10^3 Hz be greatest? The correct answer: iron metal at 25^oC See Section 12-1
3.	The fog horn of a ship echoes off an iceberg in the distance. If the echo is heard 5.00 seconds after the horn is sounded and the air temperature is - 50.0^oC, how far away is the iceberg? The correct answer: 750 m See Sections 12-1, 11-7
4.	A man drops a metal probe down a deep well drilling shaft that is 3920 meters deep. If the temperature is 25^oC, which is the closest estimate of how long it takes to hear the echo after the probe is dropped? The correct answer: 40 s See Sections 12-1, 2-7
5.	What is the intensity, in W/m^2, of sound with a sound level of 20 dB? The correct answer: 10^-10 W/m^2 See Section 12-2
6.	What is the sound level of a wave with an intensity of 10^-3 W/m^2?
7.	A stereo receiver has a power output of 50 W at a frequency of 1000 Hz. If the frequency is decreased to 100 Hz, the output decreases by 10 dB. What is the power output at 10 Hz? The correct answer: 5.0 W See Section 12-2
8.	If the intensity of a sound is increased by a factor of 10, the sound level is increased by ___ dB. The correct answer: 10 See Section 12-2
9.	If the sound level is increased 20 dB, the intensity of the sound is increased by a factor of ___. The correct answer: 100 See Section 12-2
10.	While tuning a guitar, one finds it necessary to tighten one of the strings of the guitar. As a result of tightening the string, . . . . . . the speed of a transverse wave on the string ___. Your answer: increases
11.	While tuning a guitar, one finds it necessary to tighten one of the strings of the guitar. As a result of tightening the string, . . . . . . the wavelength of the longest wavelength standing wave which can exist on the string ___. The correct answer: remains constant See Section 12-5
12.	While tuning a guitar, one finds it necessary to tighten one of the strings of the guitar. As a result of tightening the string, . . . . . . the frequency of the fundamental frequency of the string ___. The correct answer: increases See Section 12-5
13.	The longest wavelength that can exist as a standing wave on a string 2.0 m long that is tied at both ends is ___ m. The correct answer: 4.0 See Section 12-5
14.	The longest wavelength that can exist as a standing wave in an organ pipe 2.0 m long that is open on one end and closed on the other is ___ m. The correct answer: 8.0 See Section 12-5
15.	The longest wavelength that can exist as a standing wave in an organ pipe 2.0 m long that is open on both ends is ___ m. The correct answer: 4.0 See Section 12-5
16.	Two pulses, exactly out of phase, travel towards each other along a string as indicated below: The phenomenon that occurs when the pulses meet is called The correct answer: interference. See Section 12-7
17.	If two frequencies emitted from two sources are 48 and 54 vibrations per second, how many beats per second are heard? The correct answer: 6 See Section 12-7
18.	The frequency heard by a detector is higher than the frequency emitted by the source. Which of the statements below must be true? The correct answer: The source and the detector may be moving towards each other. See Section 12-8
19.	You are caught in a narrow median of a street and a small sports car is approaching you at a constant speed of 40 m/s. The engine of the car is emitting a sound at a constant frequency of 100 Hz as heard by the driver of the car. You measure the speed of the sound of the engine and determine it to be 340 m/s on this windless day. The pitch of the sound of the engine that you hear as the car approaches you is ___ 100 Hz. The correct answer: more than See Section 12-8
20.	You are caught in a narrow median of a street and a small sports car is approaching you at a constant speed of 40 m/s. The engine of the car is emitting a sound at a constant frequency of 100 Hz as heard by the driver of the car. You measure the speed of the sound of the engine and determine it to be 340 m/s on this windless day. After the car passes you and continues up the street with the same constant speed, you again measure the speed of the engine sound and find it to be ___ 340 m/s. The correct answer: equal to See Section 12-8