• # question_answer The apparent frequency of the whistle of an engine changes by the ratio 5/3 as the engine passes a stationary observer. If the velocity of sound is 340 m/s, then the velocity of the engine is- A) 340 m/s                        B) 170 m/sC) 85 m/s              D) 42.5 m/s

$\frac{n'}{n''}\,\,=\,\,\frac{V+{{V}_{S}}}{V-{{V}_{S}}}\,\,=\,\,\frac{5}{3}$ $3V+3{{V}_{S}}=5V\,\,-\,\,5{{V}_{S}}$ ${{V}_{S}}\,\,=\,\,\frac{V}{4}\,\,=\,\,\frac{340}{4}\,\,=\,\,85\,\,m/s$