According to the equation of motion under gravity v^{2} − u^{2} = 2gs

Where,

u = Initial velocity of the stone = 40 m/s

v = Final velocity of the stone = 0 m/s

s = Height of the stone

g = Acceleration due to gravity = −10 ms^{−2 }

Let h be the maximum height attained by the stone.

Therefore, 0 ^{2} − 40^{2} = 2(−10)ℎ ⇒ ℎ = (40×40) / 20 = 80

Therefore, total distance covered by the stone during its upward and downward

journey = 80 + 80 = 160 m

Net displacement during its upward and downward journey = 80 + (−80) = 0.