Q145 / 180 · COMEDK 2013 · Physics
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 $340 \mathrm{~ms}^{-1}$, then the distance between the cliffs is
- A$680 \mathrm{~m}$
- B$1700 \mathrm{~m}$
- Correct answerC$340 \mathrm{~m}$
- D$1620 \mathrm{~m}$
Solution
Let $x$ be the distance between a cliff and man, then time taken by the echo,
$$
\begin{aligned}
t &=\frac{2 x}{v}=1 \\
\Rightarrow \quad x &=\frac{v}{2}=\frac{340}{2}=170 \mathrm{~m}
\end{aligned}
$$
(given)
$\therefore$ Distance between two cliffs
$$
=2 x=2 \times 170=340 \mathrm{~m}
$$
Hence, the correct answer is option: 'C'.