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9th Class Science Sound Question Bank Sound Conceptive Objective Problems

  • question_answer
    A boy standing 70m from a high wall claps his hands. After how much time is an echo heard? (The speed of sound in air is\[\text{35}0\text{ m}{{\text{s}}^{-\text{1}}}\])

    A)  4 s                                         

    B)  0.4 s

    C)  104 s                    

    D)  1.2 s

    Correct Answer: B

    Solution :

      Distance of the boy from the wall = 70m distance travelled by sound (before echo is heard) \[=2\times 70m,\]speed of sound\[=350m{{s}^{1}}\] \[Time=\frac{distance}{speed}\] \[=\frac{2\times 70}{350}=0.4s\]


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