Question

A stone is dropped in a well of depth 500 m and a sound is heard after 45/4 seconds. Then speed of sound is (if g = 10 m/s2):

Answer 1

Answer: 400 m/s

Explanation:

Step 1: we need to find the time taken by stone to reach the bottom of well.

We will use the equation of motion:

$s=ut+0.5 at^2$

The ball was dropped, initial velocity, $u=0$

Depth of well, $s= 500 m$

The ball is falling under acceleration due to gravity, $a=g=10m/s^2$

$\Rightarrow t=\sqrt{\frac{s}{0.5a}}=\sqrt{\frac{500m}{0.5\times 10.0 m/s^2}= 10 s$

step 2: find the time in which sound travels, $t=11.25 s-10 s=1.25 s$

Step 3: Speed of sound = Distance covered/ time

Speed of sound, $v= 500 m/1.25 s=400 m/s$