Exam 14: Waves and Sound

You are driving along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind and you perceive the frequency as 1340 Hz. You are relieved that he is in pursuit of a different speeder when he continues past you, but now you perceive the frequency as 1300 Hz. What is the speed of the police car? The speed of sound in air is 343 m/s.

The wavelengths corresponding to the harmonics of an organ pipe that is open at one end and closed at the other can be found by saying that the length of the pipe must be equal to

Sound vibrations with frequencies less than 20 Hz are called

A fisherman fishing from a pier observes that the float on his line bobs up and down, taking 2.4 s to move from its highest to its lowest point. He also estimates that the distance between adjacent wave crests is 48 m. What is the speed of the waves going past the pier?

A sound source departs from a stationary observer. The frequency heard by the observer is

As the temperature of the air increases, what happens to the velocity of sound? (Assume that all other factors remain constant.)

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

Two wave pulses pass each other on a string. The one traveling toward the right has a positive amplitude, while the one traveling toward the left has an equal amplitude in the negative direction. At the point that they occupy the same region of space at the same time

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? The speed of sound in air is 343 m/s.

Sound vibrations with frequencies greater than 20,000 Hz are called

Write an expression for a harmonic wave that has an amplitude of 18 cm, a wavelength of 2.0 m, and propagates to the left at 15 m/s.

The speed of surface waves in deep water is given by v = gT/2π. What is the wavelength of a wave that has a period of 3.00 s?

Sound intensity is defined as

A ten-year exposure to the sound of a riveting machine will cause your threshold of hearing to shift from 0 dB to 30 dB. What is the sound intensity corresponding to 30 dB? The normal lowest detectable intensity is 1.0 × 10^-12 W/m².

By what amount does the intensity level decrease when you triple your distance from a source of sound?

The wavelengths corresponding to the harmonics of a string with fixed ends can be found by saying that the length of the string must be equal to

One of the harmonics of a column of air open at one end and closed at the other 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 western movies you often see a person putting his ear against the rails in the train tracks to find out if a train is approaching. Why would this give him advance knowledge of the approach of a train?

In many cartoon shows, a character runs of a cliff, realizes his predicament and lets out a scream. He continues to scream as he falls. If the physical situation is portrayed correctly, from the vantage point of an observer at the top of the cliff leaning over the edge, the pitch of the scream should be

A 15.0-m rope is pulled taut with a tension of 140 N. It takes 0.545 s for a wave to propagate along the rope. What is the mass of the rope?