To estimate the speed of sound in air suppose we choose two hills A and B about a kilometer apart. A person at the hill A fires a gun. Another person at the hill B starts a stop watch as he sees the flash of the fire and stops it on hearing the sound. Thus, he measures the time interval between the seeing of flash and hearing of the sound. Let it be t second. Then measure the distance between the hills A and B. Let it be S metre.
Experimentally, it is found that the speed of sound in air is nearly 330 m / s
