1. Tardigrade
  2. Question
  3. Physics
  4. A small source of sound vibrating at a frequency 500 Hz is rotated along a circle of radius (100/π) cm at a constant angular speed of 5 revolutions per second. The minimum and maximum frequency of the sound observed by a listener situated in the plane of the circle is (Speed of sound is 332 ms-1)

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. A small source of sound vibrating at a frequency $500\, Hz$ is rotated along a circle of radius $\frac{100}{\pi}$ cm at a constant angular speed of 5 revolutions per second. The minimum and maximum frequency of the sound observed by a listener situated in the plane of the circle is
(Speed of sound is $332 \, ms^{-1}$)

AP EAMCETAP EAMCET 2018

Solution:

The linear velocity of whistle, $v_{s}=r \omega$
$v_{s} =\frac{100}{\pi} cm \times 5\, rev / s$
$=\frac{1}{\pi} m \times 2 \pi \times 5\, rev / s =10\, m / s$
When whistle approaches the listener, then the frequency of sound heard will be maximum and minimum.
$n_{\max }=n\left(\frac{v}{v-v_{s}}\right)=500 \times \frac{332}{322}=515.5\, Hz$
$n_{\min }=n\left(\frac{v}{v+v_s}\right)=500 \times \frac{332}{342}=485.4\, Hz$