A whistle revolves in a circle with angular speed ω=20 rad/s 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 (velocity of sound =340 m/s)

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(2) 374 Hz. Given: ω=20 rad/s, r=50 cm =0.5 m, f=385 Hz, v=340 m/s. Idea: the pitch is lowest at the instant the whistle is moving directly away from the distant observer, at its full speed. vₛ=rω=0.5×20=10 m/s. Receding source: f'=f(v/(v+vₛ)). f'=385×(340)/(350). f'=374 Hz.

A whistle revolves in a circle with angular speed ω=20 rad/s 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 (velocity of sound =340 m/s)

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