Question

A man stands before a large wall at a distance of 100 m and claps his hands at regular intervals. In such way that echo of a clap merges with the next clap. If he has to clap 5 times during every 3 seconds, find the velocity of sound in air.

Answer 1

Time interval between two claps = 3/5
Time interval between to go to wall=3/10
Distance = 100m
speed= D/T
Answer= 333.33

Answer 2

Each clap must occur at the instant the echo of the last one returns. Claps occur every (3 seconds)/5 = 0.6 second. The sound travels to the wall and back, or 100+100 m = 200 m in this time (= 0.6 sec). Hence velocity (distance per unit of time) is (200 m)/(0.6 sec) = 333.33 m/sec.