Question

A stationary observer receives a sound of frequency 2000 Hz. The variation of apparent frequency and time is shown. Find the speed of source; if velocity of sound is 300 m/s:

• A. 66.6 m/s
• B. 33.3 m/s
• C. 27.3 m/s
• D. 59.3 m/s

Answer 1

The correct option is B 33.3 m/s

$ForAP,f=f_0\left(\frac{V}{V-V_{s}cos\theta }\right)ForPB,f=f_0\left(\frac{V}{V+V_{s}cos\theta }\right)$

$f_{min}=1800=f_0\left(\frac{V}{V+V_s}\right)=2000\left(\frac{V}{V+V_s}\right)f_{max}=2250=f_0\left(\frac{V}{V-V_s}\right)=2000\left(\frac{V}{V-V_s}\right)$
On solving = 33.3 m/s