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Newton's Contention

The echo of a...

Question

The echo of a gunshot is heard 8 s after the gun is fired. How far from a person is the surface that reflects the sound (velocity of sound in air = $350 m / s)$ ?

A

1400 m

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B

2800 m

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C

700 m

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D

350 m

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Solution

The correct option is B 1400 m

Suppose the distance between shooter and reflecting surface is d.

Hence time interval for hearing echo is
$t = \frac{2 d}{v}$

$\Rightarrow 8 = \frac{2 d}{350}$

$\Rightarrow d = 1400 m$

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