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(A) Given:Velocity of source (car $X$),$V_s = 36 \; km/h = 36 	imes \frac{5}{18} = 10 \; m/s$.Velocity of observer (car $Y$),$V_o = 72 \; km/h = 72 \

Vedclass · Accepted Answer

$1210$

Vedclass · Answer

(A) Given:Velocity of source (car $X$),$V_s = 36 \; km/h = 36 	imes \frac{5}{18} = 10 \; m/s$.Velocity of observer (car $Y$),$V_o = 72 \; km/h = 72 	imes \frac{5}{18} = 20 \; m/s$.Velocity of sound,$V = 340 \; m/s$.Apparent frequency,$f' = 1320 \; Hz$.Using the Doppler effect formula for source and observer approaching each other:$f' = f_0 \left( \frac{V + V_o}{V - V_s} ight)$Substituting the values:$1320 = f_0 \left( \frac{340 + 20}{340 - 10} ight)$$1320 = f_0 \left( \frac{360}{330} ight)$$1320 = f_0 \left( \frac{36}{33} ight)$$f_0 = 1320 	imes \frac{33}{36}$$f_0 = 1210 \; Hz$.Therefore,the actual frequency of the whistle is $1210 \; Hz$.

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