According to the equation of motion under gravity v2 − u2 = 2gs
Where,
u = Initial velocity of the stone = 0 m/s
v = Final velocity of the stone
s = Height of the stone = 19.6 m
g = Acceleration due to gravity = 9.8 ms−2
∴ v 2 − 02 = 2 × 9.8 × 19.6
⇒ v 2 = 2 × 9.8 × 19.6 = (19.6)2
⇒ v = 19.6 ms−1
Hence, the velocity of the stone just before touching the ground is 19.6 ms−1 .
