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JCECE Medical JCECE Medical Solved Paper-2014

  • question_answer
    Two cars are moving on two perpendicular roads towards a crossing with uniform speeds of 72 km/h and 36 km/h. If first car blows horn of frequency 280 Hz, then the frequency of  horn heard by the driver of second car when line joining the car makes angle of \[{{45}^{o}}\] with the roads, will be

    A)  321 Hz            

    B)  298 Hz

    C)  289 Hz            

    D)  280 Hz

    Correct Answer: B

    Solution :

     The component of velocity of source along line joining \[{{v}_{s}}={{v}_{1}}\cos {{45}^{o}}=36\times \frac{1}{\sqrt{2}}\] \[=5\sqrt{2}\,m/s\] Component of velocity of observer along line joining \[{{v}_{0}}={{v}_{2}}\cos {{45}^{o}}\] \[=72\,\,\times \,\frac{1}{\sqrt{2}}\] \[=10\sqrt{2}\] The frequency of horn \[n=\frac{v+{{v}_{0}}}{v-{{v}_{s}}}\] \[n=\frac{330+10\sqrt{2}}{330-5\sqrt{2}}\times 280\] \[=\frac{344}{323}\times 280=298\,Hz\]


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