Question

A man is standing in a valley between two parallel mountains. He fires a gun and hears echo at an interval of 2s and 3.5s. what is the distance between 2 mountains? (Take speed of sound = 350 m/s)

• A. 350 m
• B. 700 m
• C. 962.5 m
• D. 612.5 m

Answer 1

The correct option is C

962.5 m

Let distance from mountain 1 be $d_1$

Time taken for sound to reflect and come back is 2 sec

. distance travelled by sound = 2d,

speed = 350 m/s

$(speed=\frac{distance}{time})$

$d_1$ = 350 m

similarly for mountain 2

distance = 2$d_2$

speed = 350

time = 3.5 sec

$\frac{2d_2}{3.5}$= 350

$d_2$ = 612.5

distance between mountains will be $d_1+d_2$= 350 + 612.5

= 962.5 m