Question

A man, standing between two cliffs, claps his hands and starts hearing a series of echoes at intervals of one second. If the speed of sound in air is $340 \,ms ^{-1}$, the distance between the cliffs is ..........

• A. 340 m
• B. 1620 m
• C. 680 m
• D. 1700 m

Answer 1

Answer: (A)

340 m

Answer 2

Let the distance of man from each cliff be $x$.
Thus time taken by sound to hit a cliff and return $=\frac{2 x}{v}=1$
$\Rightarrow x =\frac{340}{2}\, m =170 \,m$
Thus distance between the cliffs $=170 \,m \times 2=340\, m$