JEE Main & Advanced Sample Paper JEE Main Sample Paper-47

  • question_answer
    Two cars are moving towards each other with same speed, if frequency of horn blown by driver of one car and frequency appeared to another driver differ by 4% from the frequency of horn, then find out speed of cars (speed of sound =300 m/s)

    A)  12 m/s            

    B)  6.6 m/s

    C)  4.2 m/s                      

    D)  5.9 m/s

    Correct Answer: D

    Solution :

     As       \[{{v}^{'}}=1.04\,v\] \[=v\left( \frac{300+{{v}_{0}}}{300-{{v}_{0}}} \right)\] \[\Rightarrow \]            \[300+{{v}_{0}}=300\times 1.04-1.04\,{{v}_{0}}\] or         \[2.04\,{{v}_{0}}=0.04\times 300\] \[\therefore \]    \[{{v}_{0}}=5.88\,m/s\simeq 5.9\,m/s\]

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