Question

police man blows a whistle calculate the changewith frequency of 500hz a car moves
towards him with velocity 15m/s calculate the change in frequency heared by driver of the car before and after crossing the police man [speed of sound in air is 300m/s]

Answer 1

Dear student,
$$\begin{gathered} fromthegivenndata \\ sourcefrequency{f}_s=500Hz \\ observedfrequency{f}_0=? \\ Sourcevelocity{V}_s=15\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right. \\ soundvelocityC=300\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right. \\ \frac{f_0}{f_s}=\frac{c}{c-V_s} \\ substitutingweobserve \\ \frac{f_0}{500}=\frac{300}{300-15} \\ {f}_0=526.31Hz \\ changeinfrequency∆f=26.31Hz \end{gathered}$$