Question

A person standing between two vertical cliffs and $320m$ away from the nearest cliff, produces sound. He hears the first echo after $4s$ and the second echo $1.5s$ later. Calculate the distance between the cliffs.

• A. 1760m
• B. 1520m
• C. 1560m
• D. 1720m

Answer 1

The correct option is A 1760m

$v=\frac{2d}{t}$

$\Rightarrow v=\frac{2\times 640}{4}=320$m\s

$\therefore v=\frac{2d}{t}$

$\Rightarrow 320=\frac{2x}{7}$

$\Rightarrow x=\frac{120\times 7}{2}=1120$m

Distance$=1120+640=1760$m