A whistle revolves in a circle with angular speed `omega` = 20 rad/sec using a string of length 50 cm . If the frequency of sound from the whistle is 385 Hz, what is the minimum frequency heard by an observer which is far away from the centre. Velocity of sound in air is 340 m/s

Options

A. 385 Hz
B. 394 Hz
C. 374 Hz
D. 333 Hz

Answer

C

Explanation

`omega = 20 ` rad/s and r = 0.5 m
`therefore U_(s) = r omega = 10 `m/s
`V_(min) ((V)/(V + U_(s))). V = (340 xx 385)/(340 + 10) = 374 Hz.`
Correct choice is (C).