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JCECE Medical JCECE Medical Solved Paper-2010

  • question_answer
    Two trains are moving towards each other with speeds of 20 m/s and 15 m/s relative to the ground. The first train sounds a whistle of frequency 600 Hz, the frequency of the whistle heard by a passenger in the second train before the train meets is (the speed of sound in air is 340 m/s)

    A)  600 Hz         

    B)  585 Hz

    C)  645 Hz          

    D)  666 Hz

    Correct Answer: D

    Solution :

     The perceived frequency \[(f)\] is related to the actual frequency \[({{f}_{0}})\] and the relative speeds of the source \[({{v}_{s}}).\]and observer \[({{v}_{o}})\] and the speed \[(v)\] of waves in the medium is given by \[f={{f}_{o}}\left( \frac{v+{{v}_{o}}}{v-{{v}_{s}}} \right)\] Give\[v=340\,m/s,\,{{v}_{o}}=15\,m/s,\,{{v}_{s}}=20\,m/s\] \[\therefore \] \[f=600\times \left( \frac{340+15}{340-20} \right)\] \[=\frac{355}{320}\times 600=666\,Hz\]


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