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9th Class Science Sound Question Bank Sound Formative Objective Problems

  • question_answer
    A boy stands 85m in front of a high wall and then blows a whistle. Calculate the time interval when he hears an echo. (speed of sound = 340 m/s)

    A)  0.5s      

    B)  5s  

    C)  1.5s                      

    D)  2s

    Correct Answer: A

    Solution :

      Distance between the wall and the boy i.e.,\[d=85\text{ }m\] speed of sound (v) = 340 m/s time, (t) = ? We know, \[v=\frac{2d}{t}\] \[\Rightarrow \] \[340=\frac{2\times 85}{t}\] \[\Rightarrow \] \[t=\frac{2\times 85}{340}=0.5\,s\]                       


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