Question

A girl clapped her hands standing near a cliff and heard the echo after 4 seconds. If the speed of sound in air be 340 m/s then, the distance of the cliff from the girl should be

Answer 1

The distance between the girl and the cliff is 680 m

-Echo is heard only if the distance is more than 17 m. This helps a little for our verification

-The sound of the clap needs to travel to the cliff , get reflected and travel back the same distance in order for the girl to hear it. Hence if the distance between the girl and the cliff is d, the sound travels a total distance of 2.d

-The time taken by the sound to travel 2.d distance is given as 4 seconds.

-We apply the formula, distance = speed * time

Here, distance = 2.d m

         speed = 340 m/s

         time = 4 s

-Therefore, 2.d=340*4

on solving for d, we get d = 680 m