Question

A stone is dropped into a well 80m deep and the impact of sound is heard after
4.22s. What is the velocity of sound in air ? (Take g = 10 m/s^2)​

Answer 1

Given that, u = 0 m/s (as the stone was dropped)

A stone is dropped into a well 80m deep and the impact of sound is heard after 4.22s.

distance (s) = 80 m, time = 4.22 sec and g = 10 m/s²

Now, time taken by stone to reach the bottom.

s= ut + 1/2 at²

80 = 0(t) + 1/2(10)t²

80 = 0 + 1/2 × 10 × t²

80 = 5t²

16 = t²

4 = t (negative in can't be negative. So, negative one neglected)

Therefore, stone takes 4 sec to reach the bottom.

Now,

Time taken by the stone to produce the sound = 4.22 - 4 = 0.22 sec

Speed = Distance/Time

Speed = 80/0.22 = 363.64

Therefore, the speed (velocity) of sound in air is 363.64 m/s.