Question

A table is revolving on its axis at 5 revolutions per second. A sound source of frequency $1000\text{Hz}$ is fixed on the table at $70\text{cm}$ from the axis. The minimum frequency heard by a listener standing far away from the table will be (speed of sound $=352\text{m/s})$

• A. $1000\text{Hz}$
• B. $1066\text{Hz}$
• C. $941\text{Hz}$
• D. $352\text{Hz}$

Answer 1

The correct option is C $941\text{Hz}$

Velocity of source is $v_S=r\omega =0.70\times 2\pi \times 5=22\text{m /s}$

Minimum frequency is heard when the source is receding the man, it is given by $n_{min}=n\frac{v}{v+v_s}=1000\times \frac{352}{352+22}=941\text{Hz}|$