$A$ stone is dropped from the roof of a building. It takes $4 \, s$ to reach the ground. Find the height of the building. $(g = 9.8 \, m \, s^{-2})$

(78.4 M) Given: Initial velocity $u = 0 \, m \, s^{-1}$,time $t = 4 \, s$,and acceleration due to gravity $g = 9.8 \, m \, s^{-2}$.
Using the second equation of motion for free fall:
$h = ut + \frac{1}{2}gt^2$
Substituting the values:
$h = (0 \times 4) + \frac{1}{2} \times 9.8 \times (4)^2$
$h = 0 + 0.5 \times 9.8 \times 16$
$h = 4.9 \times 16$
$h = 78.4 \, m$
Thus,the height of the building is $78.4 \, m$.