**Solution :**

In question it is given that —

Initial velocity, u = 0

Final velocity, v = ? (To be calculated)

Acceleration due to gravity, g = 9.8 m/s2 (Stone comes down)

And,

Height, h = 19.6 m

**v**^{2} = u^{2} + 2gh

v^{2} = (0)^{2} + 2 x 9.8 x 19.6

v^{2}= 19.6 x 19.6

v^{2} = (19.6)^{2}

**v = 19.6 m/s**

So, the velocity of stone just before hitting the ground will be **19.6 metres per second**.