Two children are at opposite ends of an aluminium rod. One strikes the end of the rod with a stone. Find the ratio of time taken by the sound waves in air and in aluminium to reach the second child. Take velocity of sound in aluminium equal to 6420 m`s^(-1)` stand velocity of sound in air as 346 ms.)

Explanation

Let the length of the aluminium rod be 1 m
Let `t_(1)` be the time taken by the sound to travel through distance l in air,
`t_(1)=("distance")/("Speed")=(1)/(v_("sir"))`…………(1)
Let `t_(2)` be the time taken by the sound to travel through distance l in aluminium rod,
`t_(2)=("distance")/("speed")=(l)/(v_(al))`...........(2)
From (1) and (2)
`(t_(1))/(t_(2))=(6420 ,s^(-1))/(346 ms^(-1))=18.55`