Q: A man standing between two cliffs hears the first echo of a sound after 2 sec and the second echo 3 sec after the initial sound. If the speed of sound be 330 m/s, the distance between the two cliffs should be:
(a) 1650 m
(b) 990 m
(c) 825 m
(d) 660 m
Ans: (c)
Sol:speed of sound v = 330 m/s
Let d = distance between two cliffs
and x = distance of man from first cliff then distance of man from 2nd cliff = d-x
$\large \frac{2x}{v} = 2$ …(i)
$\large \frac{2(d-x)}{v} = 3 $ …(ii)
On solving we get ,
d = 825 m