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JCECE Medical JCECE Medical Solved Paper-2012

  • question_answer
    An engine approaches a hill with a constant speed. When it is at a distance of 0.9 km, it blows a whistle, whose echo is heard by the driver after 5 s. If speed of sound in air is 330 m/s, the speed of engine is

    A)  10 m/s

    B)  20 m/s          

    C)  30 m/s

    D)  40 m/s

    Correct Answer: C

    Solution :

     If the speed of engine is\[v,\]the distance travelled by engine in 5 s will be 5v and hence the distance travelled by sound in reaching the hill and coming back to the moving driver \[=900+(900-5v)\] \[=1800-5v\] So, the time interval between original sound and ifs echo \[t=\frac{(1800-5v)}{330}=5\] \[\Rightarrow \] \[v=30\,m/s\]


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