Exam 16: Waves and Sound

The displacement of a vibrating string versus position along the string is shown in the figure.The periodic waves have a speed of 10.0 cm/s.A and B are two points on the string. -What is the difference in phase between the points A and B?

When one person was talking in a small room, the sound intensity level was 60 dB everywhere within the room.Then, there were 14 people talking in similar manner simultaneously in the room, what was the resulting sound intensity level?

Which one of the following statements concerning waves is false?

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

Determine the speed of the wave.

A periodic wave is produced on a stretched string.Which one of the following properties is not related to the speed of the wave?

A stationary railroad whistle is sounded.An echo is heard 5.0 seconds later by the train's engineer.If the speed of sound is 343 m/s, how far away is the reflecting surface?

16-2 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 lowest frequency for the sound from the whistle?

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.

What is the wavelength of the sound in the direction of motion of the car?

16-3 The car in the drawing is moving to the left at 35 m/s.The car's horn continuously emits a 2.20 × 10² Hz sound.The figure also shows the first two regions of compression of the emitted sound waves.The speed of sound is 343 m/s. -How far does the car move in one period of the sound emitted from the horn?

A transverse wave is traveling in the -x direction on a string that has a linear density of 0.011 kg/m.The tension in the string is 7.4 N.The amplitude of the wave is 0.017 m; and its wavelength is 1.5 m.Which one of the following is the correct equation for the displacement of a particle from its equilibrium position?

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?

Two motorcycles are traveling in opposite directions at the same speed when one of the cyclists blasts his horn, which has frequency of 544 Hz.The other cyclist hears the frequency as 522 Hz.If the speed of sound in air is 344 m/s, what is the speed of the motorcycles?

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

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?

The Young's modulus of aluminum (density = 2700 kg/m³) is 6.9 × 10¹⁰ N/m².Determine the speed of sound in an aluminum rod.

Which one of the following waves is purely longitudinal?

Two children setup a "telephone" by placing a long, slender aluminum (Y = 6.9 × 10¹⁰ N/m²) rod that has a length of 6.1-m between their two houses.To communicate, a child taps a coded message on one end.How long do the sound waves take to reach the other end? Note: the density of aluminum is 2700 kg/m³.

The speed of sound in a certain metal block is 2.00 × 10³ m/s.The graph shows the amplitude (in meters) of a wave traveling through the block versus time (in milliseconds).What is the wavelength of this wave?