NEET Sample Paper NEET Sample Test Paper-50

  • question_answer 5) 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/s

    C) 85 m/s              

    D) 42.5 m/s

    Correct Answer: C

    Solution :

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

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