A whistle S emitting a steady note of frequency moves towards a stationary observer O…
PHYSICS · Subjective · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics
Problem
A whistle S emitting a steady note of frequency 680Hz moves towards a stationary observer O with a speed of 30m s−1. Simultaneously, a second whistle W emitting a steady note of frequency 682Hz moves away from the observer with a speed of 20m s−1. The speed of sound in air may be taken as 340m s−1.
(i) Calculate the apparent frequencies heard by the observer due to S and W separately.
(ii) Hence determine the number of beats heard per second by the observer.
(iii) If both whistles suddenly come to rest at the same instant, what will be the new beat frequency heard? Justify your answer.