A whistle revolves in a circle with angular speed ω=20 rad s^ -1 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

Correct answer: B. 375 ~Hz Velocity of source is given as gathered V_ source = rus =0.5 ×20 =10 ~ms^ -1 gathered Minimum frequency is f ~min aligned & =((V)/(V+V_s))f & =(340)/(340+10) ×385=374 ~Hz aligned

NEET 2002

Exam: NEET
Year: 2002
Subject: Physics
Chapter: Waves and Sound

NEET 2002 · Physics · Waves and Sound

A whistle revolves in a circle with angular speed ω=20 rad s^ -1...

A whistle revolves in a circle with angular speed

\omega=20 \mathrm{rad} \mathrm{s}^{-1}

using a string of length

50 \mathrm{~cm}. If the frequency of sound from the whistle is

385

\mathrm{~Hz}

, then what is the minimum frequency heard by an observer which is away from the centre

\left(v_{\text{sound }}=340 \mathrm{~ms}^{-1}\right)

A whistle revolves in a circle with angular speed ω=20 rad s^ -1 using a string of length 50 ~cm. If the frequency of

Options

A $385 \mathrm{~Hz}$
B $375 \mathrm{~Hz}$
C $394 \mathrm{~Hz}$
D $333 \mathrm{~Hz}$

Correct answer

B. $375 \mathrm{~Hz}$

Step-by-step solution

Velocity of source is given as

\begin{gathered}V_{\text{source }}=\text{ rus }=0.5 \times20 \\ =10 \mathrm{~ms}^{-1} \end{gathered}\therefore

Minimum frequency is

f \mathrm{~min}

\begin{aligned}& =\left(\frac{V}{V+V_s}\right)f \\ & =\frac{340}{340+10} \times385=374 \mathrm{~Hz} \end{aligned}

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