A jet engine emits a whine of frequency 3000 Hz.When the engine is moving directly away from an observer at half the speed of sound,an observer hears a frequency of
A)1000 Hz
B)1500 Hz
C)2000 Hz
D)4500 Hz
E)6000 Hz

Question

Quizplus · Accepted Answer

The Doppler effect formula for sound when the source is moving away is f' = f * (v / (v + vs)), where f is the source frequency, v is the speed of sound, and vs is the speed of the source. Here, vs = 0.5v, so f' = 3000 * (v / (v + 0.5v)) = 3000 * (v / 1.5v) = 3000 * (2/3) = 2000 Hz.

A Jet Engine Emits a Whine of Frequency 3000 Hz