Exam 21: Mechanical Waves

One of the harmonics of a column of air in a tube that is open at both ends has a frequency of 448 Hz,and the next higher harmonic has a frequency of 576 Hz.What is the fundamental frequency of the air column in this tube?

If a string fixed at both ends resonates in its fundamental mode with a frequency of 150 Hz,at which of the following frequencies will it not resonate? (There could be more than one correct choice.)

A wire that is 1.0 m long with a mass of 90 g is under a tension of 710 N.When a transverse wave travels on the wire,its wavelength is 0.10 m and its amplitude is 6.5 mm.What is the frequency of this wave?

A string that is 0.26 m long is vibrating in its n = 6 harmonic.The sound from this string excites a pipe that is $0.88 \mathrm {~m}$ long and open at both ends into its second overtone resonance.What is the common resonant frequency of the string and the pipe? The speed of sound in air is 345 m/s.

A certain factory whistle can be heard up to a distance of 2.5 km.Assuming that the acoustic output of the whistle is uniform in all directions,how much acoustic power is emitted by the whistle? The threshold of human hearing is 1.0 × 10^-12 W/m².

What is the frequency of a pressure wave of wavelength 2.5 m that is traveling at 1400 m/s?

What is the frequency does a stationary observer hear when a train approaches her with a speed of 30 m/s.The frequency of the train horn is 0.600 kHz and the speed of sound is 340 m/s.

What characteristics of a sound wave are related to the "pitch" of a musical note? (There could be more than one correct choice.)

Two speakers are placed side by side and driven by the same frequency of 0.50 kHz.If the distance from a person to one speaker is 5.0 m and the person detects little or no sound,which of the following is a possible the distance from the person to the other speaker? The sound speed in the room is 340 m/s.

What is the ratio of the intensities of two sounds with intensity levels of 70 dB and 40 dB?

When a certain string is under tension T,the speed of a wave in the string is v.What will be the speed of a wave in the string if the tension is increased to 2T without changing the mass or length of the string?

The intensity level is 65 dB at a distance 5.00 m from a barking dog.What would be a reasonable estimate for the intensity level if two identical dogs very close to each other were barking? You can ignore any interference effects.

A string fixed at both ends is vibrating in one of its harmonics.If we now increase only the frequency at which the string is vibrating,which of the following characteristics do we also increase? (There could be more than one correct choice.)

What is the frequency of the fundamental mode of vibration of a steel piano wire stretched to a tension of 440 N? The wire is 0.600 m long and has a mass of 5.60 g.

Four waves are described by the following equations,where distances are measured in meters and times in seconds. I.y = 0.12 cos(3x - 21t) II.y = 0.15 sin(6x + 42t) III.y = 0.13 cos(6x + 21t) IV.y = -0.23 sin(3x - 42t) Which of these waves have the same speed?

As you stand by the side of the road,a car approaches you at a constant speed,sounding its horn,and you hear a frequency of 76 Hz.After the car goes by,you hear a frequency of 65 Hz.What is the speed of the car? The speed of sound in the air is 343 m/s.

The speed of sound through the ground is about 6.0 km/s while the speed of sound in air is 343 m/s.A very powerful explosion occurs some distance away and you feel the ground vibrate 60 seconds before you hear the sound of the explosion.How far away is the explosion?

A music tuner uses a 554-Hz C# tuning fork to tune the frequency of a musical instrument.If the tuner hears a beat frequency of 2 Hz,what is the frequency of the instrument?

A 4.0-g string is 0.39 m long and is under tension.The string vibrates at 600 Hz in its third harmonic.What is the tension in this string?

You double your distance from a sound source that is radiating equally in all directions.What happens to the intensity of the sound? It reduces to