18. Waves & Sound

(II) Two trains emit 508-Hz whistles. One train is stationary. The conductor on the stationary train hears a 4.5-Hz beat frequency when the other train approaches. What is the speed of the moving train?1

Two loudspeakers face each other at opposite ends of a long corridor. They are connected to the same source which produces a pure tone of 315 Hz. A person walks from one speaker toward the other at a speed of 1.6 m/s. What “beat” frequency does the person hear?

(II) A police car sounding a siren with a frequency of 1580 Hz is traveling at 120.0 km/h .

(b) What siren frequencies are heard in a car traveling at 90.0 km/h in the opposite direction before and after passing the police car?

(III) A factory whistle emits sound of frequency 770 Hz. The wind velocity is 15.0 m/s from the north (heading south). What frequency will observers hear who are located, at rest,

(d) due west, of the whistle?

(III) A factory whistle emits sound of frequency 770 Hz. The wind velocity is 15.0 m/s from the north (heading south). What frequency is heard by a cyclist heading

(e) north, toward the whistle at 12.0 m/s? Assume T = 20 °C .

(III) A factory whistle emits sound of frequency 770 Hz. The wind velocity is 15.0 m/s from the north (heading south). What frequency will observers hear who are located, at rest,

(a) due north, of the whistle?

(III) A factory whistle emits sound of frequency 770 Hz. The wind velocity is 15.0 m/s from the north (heading south). What frequency is heard by a cyclist heading

(f) west, toward the whistle at 12.0 m/s? Assume T = 20 °C .

(II) A police car sounding a siren with a frequency of 1580 Hz is traveling at 120.0 km/h .

(c) The police car passes a car traveling in the same direction at 80.0 km/h. What two frequencies are heard in this car?

(III) A factory whistle emits sound of frequency 770 Hz. The wind velocity is 15.0 m/s from the north (heading south). What frequency will observers hear who are located, at rest,

(b) due south, of the whistle?

(III) A factory whistle emits sound of frequency 770 Hz. The wind velocity is 15.0 m/s from the north (heading south). What frequency will observers hear who are located, at rest,

(c) due east, of the whistle? and