Exam 16: Waves and Sound

A car moving at 35 m/s approaches a stationary whistle that emits a 220 Hz sound. The speed of sound is 343 m/s. What is the speed of the sound relative to the driver of the car?

A periodic transverse wave is established on a string such that there are exactly two cycles traveling along a 3.0-m section of the string. The crests move at 20.0 m/s. -What is the shortest horizontal distance from a crest to a point of zero acceleration?

A physics student is asked to determine the length of a long, slender, copper bar by measuring the time required for a sound pulse to travel the length of the bar. The Young's modulus of copper is 1.1 × 10¹¹ N/m²; and its density is 8890 kg/m³. The student finds that the time for the pulse to travel from one end to the other is 5.6 × 10^-4 s. How long is the rod?

A bell is ringing inside of a sealed glass jar that is connected to a vacuum pump. Initially, the jar is filled with air. What does one hear as the air is slowly removed from the jar by the pump?

A wave has a frequency of 58 Hz and a speed of 31 m/s. What is the wavelength of this wave?

A certain string on a piano is tuned to produce middle C (f = 261.63 Hz) by carefully adjusting the tension in the string. For a fixed wavelength, what is the frequency when this tension is tripled?

A periodic wave travels along a stretched string in the direction shown by the arrow. The sketch shows a "snapshot" of the pulse at a certain instant. Points A, B, and C are on the string. Which entry in the table below correctly describes how particles of string between A and B and between B and C are moving? between A and B between B and C

An unstretched spring has a length of 0.30 m. When the spring is stretched to a total length of 0.60 m, it supports traveling waves moving at 4.5 m/s. How fast will waves travel on this spring if it is stretched to 0.90 m?

A transverse periodic wave on a string with a linear density of 0.200 kg/m is described by the following equation: y = 0.08 sin(469t - 28.0x), where x and y are in meters and t is in seconds. What is the tension in the string?

Two boys are whispering in the library. The radiated sound power from one boy's mouth is 1.2 × 10^-9 W; and it spreads out uniformly in all directions. What is the minimum distance the boys must be away from the librarian so that she will not be able to hear them? The threshold of hearing for the librarian is 1.00 × 10^-12 W/m².

The diagram shows the various positions of a child in motion on a swing. Somewhere in front of the child a stationary whistle is blowing. -At which position(s) will the child hear the highest frequency for the sound from the whistle?

The decibel level of a jackhammer is 130 dB relative to the threshold of hearing. Determine the decibel level if three jackhammers operate side by side.

Of the three traveling waves listed below, which one(s) is(are) traveling in the +x direction?

A periodic traveling wave is generated on a string of linear density 8.0 × 10-4 kg/m. Figure A shows the displacements of the particles in the string as a function of the position x along the string at t = 0 s. Figure B shows the displacement of the particle at x = 0 m as a function of time. The particle positions are measured from the left end of the string (x = 0 m) and the wave pulses move to the right. -Determine the speed of the wave.

A periodic traveling wave is generated on a string of linear density 8.0 × 10-4 kg/m. Figure A shows the displacements of the particles in the string as a function of the position x along the string at t = 0 s. Figure B shows the displacement of the particle at x = 0 m as a function of time. The particle positions are measured from the left end of the string (x = 0 m) and the wave pulses move to the right. -What is the tension in the string?

The decibel level of a jackhammer is 125 dB relative to the threshold of hearing. Determine the sound intensity produced by the jackhammer.

A transverse periodic wave is established on a string. The wave is described by the expression where y is in meters when x and t are in meters and seconds, respectively. If the wave travels with a speed of 20.0 m/s, what is its frequency, f?

A loudspeaker at the base of a cliff emits a pure tone of frequency 3000.0 Hz. A man jumps from rest from the top of the cliff and safely falls into a net below. How far has the man fallen at the instant he hears the frequency of the tone as 3218.0 Hz? The speed of sound is 343 m/s.

According to US government regulations, the maximum sound intensity level in the workplace is 90.0 dB. Within one factory, 32 identical machines produce a sound intensity level of 92.0 dB. How many machines must be removed to bring the factory into compliance with the regulation?

A wave is traveling at 35 m/s on a string with a linear density of 0.082 kg/m. What is the tension in the string?