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A whistle revolves in a circle with an a...

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

A

394 Hz

B

385 Hz

C

374 Hz

D

333 Hz

Text Solution

Verified by Experts

The correct Answer is:
C
The velocity of the whistle (source)
`v_(s) = r omega = 0.5 xx 20 = 10 m//s and v = 340 m//s`

When the whistle is at , the frequency of the whistle heard y the observer is minimum.
`n_("apparent") = ((v)/(v + v_(s))) xx n = ((340)/(340 + 10)) xx 385`
`= (34)/(35) xx 385 = 34 xx 11 = 374 Hz`
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