Exam 14: Waves and Sound

Two wave pulses with equal positive amplitudes pass each other on a string. One is traveling toward the right and the other toward the left. At the point that they occupy the same region of space at the same time

The vertical displacement of a string is given by y(x,t) = (6.00 mm) cos[(3.25 m^-1)x - (7.22 s^-1)t]. What is the wavelength of the wave?

An organ pipe, open at both ends, is 5.20 m long. What is its fundamental frequency? The speed of sound in air is 343 m/s.

The vertical displacement of a string is given by y(x,t) = (6.00 mm) cos[(3.25 m^-1)x - (7.22 s^-1)t]. What is the speed of the wave?

Consider a closed pipe of length L. What are the wavelengths of the three lowest tones produced by this pipe?

If the intensity level of one trombone is 70 dB and that of one cornet is 65 dB, which is louder: 76 trombones or 110 cornets?

Give at least one example of each of the following: (a) longitudinal standing wave. (b) transverse standing wave.

Four waves are described by the following expressions, 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 period?

Which part of a vibrating string experiences the maximum acceleration?

Two steel wires are stretched with the same tension. The first wire has a diameter of 0.610 mm and the second wire has a diameter of 0.910 mm. If the speed of waves traveling along the first wire is 54.0 m/s, what is the speed of waves traveling along the second wire?

You drop a stone down a well. You hear the splash 1.63 s later. How deep is the well? The speed of sound in air is 343 m/s.

In order to produce beats, the two sound waves should have

A factory siren indicating the end of a shift has a frequency of 90.0 Hz. (a) What frequency is perceived by the occupant of a car traveling towards the factory at 25 m/s? (b) What frequency is perceived by the occupant of a car traveling away from the factory at 30 m/s?

Infrasound carries over long distances better than ultrasound.

An earthquake generates three kinds of waves: surface waves (L-waves), which are the slowest and weakest, shear (S) waves, which are transverse waves and carry most of the energy, and pressure (P) waves, which are longitudinal waves and are the fastest. The speed of P waves is approximately 7 km/s, and that of S waves is about 4 km/s. People do not generally feel the P waves, but animals seem to be sensitive to them. If a person reports that her dog started barking 20 seconds "before the earthquake," then approximately how far was the origin of the earthquake?

Two strings of identical mass and length are stretched with their ends fixed, but the tension in one string is 1.10 times greater than in the other. Waves on the string with the lower tension propagate at 35.2 m/s. The fundamental frequency of that string is 258 Hz. What is the beat frequency when each string is vibrating at its fundamental frequency?

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?

By what amount does the intensity level increase when you triple the intensity of a source of sound?

Two in-phase loudspeakers that emit sound with the same frequency are placed along a wall and are separated by a distance of 5.00 m. A person is standing 12.0 m away from the wall, equidistant from the loudspeakers. When the person moves 1.00 m parallel to the wall, she experiences destructive interference for the first time. What is the frequency of the sound? The speed of sound in air is 343 m/s.

What is the audible range of sound frequencies?