Question:
Two trains are moving towards each other with speeds of 20 m/s and 15 m/s relative to the ground. The first train sounds a whistle of frequency 600 Hz, the frequency of the whistle heard by a passenger in the second train before the train meeets is (the speed of sound in air is 340 m/s)
Two trains are moving towards each other with speeds of 20 m/s and 15 m/s relative to the ground. The first train sounds a whistle of frequency 600 Hz, the frequency of the whistle heard by a passenger in the second train before the train meeets is (the speed of sound in air is 340 m/s)
Updated On: Jun 20, 2022
- 600 Hz
- 585 Hz
- 645 Hz
- 666 Hz
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The Correct Option is D
Solution and Explanation
The perceived frequency (f')
$ \hspace20mm f' = f_0 \bigg( \frac{v + v_0}{v - v_s}\bigg)$
Given, $ v = 340\, m/s, v_0 = 15\, m/s$ and $v_s = 20 m/s $
$\therefore \hspace20mm f' = 600 \times \bigg( \frac{340+ 15}{340 -20}\bigg)$
$ \hspace30mm =\frac{355}{320} \times 600\, Hz $
$ \hspace20mm f' = f_0 \bigg( \frac{v + v_0}{v - v_s}\bigg)$
Given, $ v = 340\, m/s, v_0 = 15\, m/s$ and $v_s = 20 m/s $
$\therefore \hspace20mm f' = 600 \times \bigg( \frac{340+ 15}{340 -20}\bigg)$
$ \hspace30mm =\frac{355}{320} \times 600\, Hz $
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