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Physics

A man standing 48 m away from a wall fires a gun. Calculate the time after which an echo is heard. (The speed of sound in air is 320 ms-1).

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Answer

As we know,

Speed of sound (V)=Total distance travelled (2d)time interval (t)\text {Speed of sound (V)} = \dfrac{\text{Total distance travelled (2d)}}{\text {time interval (t)}} \\[0.5em]

Total distance travelled by the sound in going and then coming back = 2d

Given,

d = 48 m

V = 320 ms-1

Substituting the values in the formula above, we get,

320=2×48tt=2×48320t=0.30s320 = \dfrac{2 \times 48}{t} \\[0.5em] t = \dfrac{2 \times 48}{320} \\[0.5em] t = 0.30 s \\[0.5em]

Hence, time after which echo is heard = 0.30 s.

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