Question

A stone is dropped from top of a tower 500 m gh into a pond of water at the base of tower .When is the splash heard at the top ?Given g=10m/sand speed of sound is 340m/s

Answer 1

the stone is dropped , so initial velocity or u = 0

also given
distance, s= 500m and g = 10m/s^2

applying the formula
$s = ut + \frac{1}{2} \times a \times {t}^{2}$
we have

$t = \sqrt{ \frac{2 \times s}{g} }$
or
$t = \sqrt{ \frac{2 \times 500}{10} } = \sqrt{100} = 10s$
this is the time required by the rock to reach the water surface, Now the time required by the sound to reach the observer is :

$t = \frac{distance}{speed}$
or to = 500÷340 = 1.47 s

so total time required is : 10 + 1.47 = 1.47s