Question

A stone is dropped into a well 44m deep and the sound of splash is heard after 3.12sec. find the speed of sound in air (g=9.8m per sec)

Answer 1

First the stone will go 44 meters down and hit the water surface. Then the splash sound will travel in from the water surface to the point from where stone is dropped. The total time taken is 3.12 second.
Let the stone reached the water surface in the well in t second.
$s=ut+0.5g{t}^2\Rightarrow 44=0+0.5\times 9.81\times t^2\Rightarrow 44=4.905t^2\Rightarrow t^2=\frac{44}{4.905}=8.97\Rightarrow t=\sqrt{8.97}=2.99s$
Time taken by sound to travel 44m =3.12 -2.99 =0.13s
speed of sound in air =$\frac{44}{0.13}=338.46m/s$