Question

a stone is thrown vertically upward with an initial velocity of 20 metre per second after how long will the stone strike the ground​

Answer 1

$\large{\implies{Amswer}}$

Time taken by the stone to attain the highest height

$v = u + at \\ 0 = 20 + ( - 9.8)t \\ - 20 = (- 9.8)t \\ \frac{ - 20}{9.8} = t$

$\large{\implies{2s(approx)}}$

The time taken by the stone to attain the highest height is equal to the time taken by the stone to come to the ground

So we have

✏ 2s+2s=4s

The stone will take 4second to strike the ground