A person standing between two vertical cliffs and 640m away from … - Vidyadip

MCQ

A person standing between two vertical cliffs and 640m away from the nearest cliff shouted. He heard the first echo after $4$ seconds and the second echo $3$ seconds later. What is the distance between the cliffs$?$

A
$1570m$
✓
$1760m$
C
$1520m$
D
$1225m$

✓

Answer

Correct option: B.

$1760m$

$\text{v}=\frac{2\text{d}}{\text{t}}$
$\Rightarrow\text{v}=\frac{2\times640}{4}=320\text{m/ s}$
$\therefore\text{v}=\frac{2\text{d}}{\text{t}}$
$\Rightarrow320=\frac{2\text{x}}{7}$
$\text{x}=1120\text{m}$
Distance $=1120+640$
$=1760\text{m}$

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