A train sounding a whistle of frequency 510 , | vedclass

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Question

(A) Given:Frequency of source $(n_0) = 510 \,Hz$.Velocity of source $(v_s) = 72 \,km/hr = 72 	imes \frac{5}{18} = 20 \,m/s$.Velocity of sound in air

Vedclass · Accepted Answer

$544, 480$

Vedclass · Answer

(A) Given:Frequency of source $(n_0) = 510 \,Hz$.Velocity of source $(v_s) = 72 \,km/hr = 72 	imes \frac{5}{18} = 20 \,m/s$.Velocity of sound in air $(v) = 320 \,m/s$.$(1)$ When the source is approaching a stationary listener,the apparent frequency $(n_1)$ is given by:$n_1 = n_0 \left( \frac{v}{v - v_s} ight)$$n_1 = 510 	imes \left( \frac{320}{320 - 20} ight) = 510 	imes \left( \frac{320}{300} ight) = 544 \,Hz$.$(2)$ When the source is moving away from a stationary listener,the apparent frequency $(n_2)$ is given by:$n_2 = n_0 \left( \frac{v}{v + v_s} ight)$$n_2 = 510 	imes \left( \frac{320}{320 + 20} ight) = 510 	imes \left( \frac{320}{340} ight) = 480 \,Hz$.Thus,the frequencies are $544 \,Hz$ and $480 \,Hz$.

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