Exam 14: Waves and Sound

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 frequency of the sound emitted by the horn? The speed of sound in the air is 343 m/s.

An organ pipe open at both ends has a length of 0.80 m.If the velocity of sound in air is What is the frequency of the second harmonic of this pipe?

What is the intensity level in decibels of a sound with intensity 10^-3 W/m²? The threshold of human hearing is 1.0 × 10^-12 W/m².

Consider a pipe of length L that is open at one end and closed at the other end.What are the wavelengths of the three lowest-pitch tones produced by this pipe?

You drop a stone down a well that is 9.5 m deep.How long is it before you hear the splash? The speed of sound in air is 343 m/s and air resistance is negligible.

Which one of the curves shown in the figure best represents the variation of wave speed v as a function of tension for transverse waves on a stretched string?

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 period?

What is the frequency of the wave shown in the figure?

Seven seconds after a brilliant flash of lightning,thunder shakes the house.Approximately how far was the lightning strike from the house?

Find the speed of an ocean wave whose displacement is given by the equation Where x and y are in meters and t is in seconds.

The wavelengths of the sounds produced by two horns are 6.0 m and 7.0 m,respectively.What beat frequency is heard when the horns are sounded on a day when the speed of sound is 340 m/s?

At a distance of 15.0 m from a sound source,the intensity level is 60.0 dB.What is the intensity level (in decibels)at a point 2.00 m from the source if the source radiates equally in all directions?

Two people are talking at a distance of 3.0 m from where you are,and you measure the sound intensity as 1.1 × 10^-7 W/m².Another student is 4.0 m away from the talkers.Calculate a reasonable estimate for the sound intensity that the other student measures.

A barking dog delivers about 1.0 mW of power,which is assumed to be uniformly distributed in all directions.What is the intensity level in decibels at a distance 5.00 m from the dog? The threshold of human hearing is 1.0 × 10^-12 W/m².

The speed of propagation of a transverse wave on a 2.0-m long string fixed at both ends is 200 m/s.Which one of the following is not a resonant frequency of this string?

Two strings both vibrate at exactly 819 Hz.The tension in one of them is then increased slightly.As a result,six beats per second are heard when both strings vibrate.What is the new frequency of the string that was tightened?

A 90-gram wire that is 1.0 m long is under tension.When a transverse wave of frequency 890 Hz travels down the wire,its wavelength is 0.10 m and its amplitude is 6.5 mm.What is the tension in the wire?

A policeman in a stationary car measures the speed of approaching cars by means of an ultrasonic device that emits a sound with a frequency of 39.6 kHz.A car is approaching him at a speed of 35.0 m/s.The wave is reflected by the car and interferes with the emitted sound producing beats.What is the frequency of the beats when the speed of sound in air is 343 m/s?

A 0.588-m string is tightly clamped at both ends.If the lowest standing wave frequency of the string is 326 Hz. How fast do waves travel on this string?

A stretched string is observed to have four equal segments in a standing wave driven at a frequency of 480 Hz.What driving frequency will set up a standing wave with five equal segments?