Question

A stone is dropped from the roof of a building. It takes 4s to reach the ground. Find the height of the building. g=9.8m/s

Answer 1

Here u=0
t=4s
g=9.8m/s2

We know that s=ut+1/2atsqaure
                         =0*4+1/2 9.8*16
                          =78.4m
Hope it helps!

Answer 2

$\red{\huge {\bf{\underline{\underline{Answer:}}}}}$

$\huge{\pink{\green {\sf{\therefore\:Height\:=\:78.4\:m}}}}$

$\red{\bf{\underline {Given:}}}$

$⟹\blue{\bold{Initial \:velocity\: of \:object, \:u\: =\: 0}}$

$⟹\blue{\bold{Acceleration \:due\: to \:gravity, \:g = 9.8\: m\: {s}^{-2}}}$

$⟹\blue{\bold{Time, \:t = 4\: s}}$

$\red{\bf{\underline {To\:Find:}}}$

$⟹ \blue{\bold{The\: height\: of \:building \:=\: \:?}}$

$\red{\huge {\bf{\underline{\underline{Step\: by\: step \:explanation:}}}}}$

$\red{\bold{We\: know\: that,}}$

$\blue {\bold{{h} = ut + \dfrac{1}{2}gt^2}}$

$\red{\bold{Substituting\: the\: values,\: we \:get}}$

$\blue{\bold{h = \dfrac{1}{2}×9.8×16 = 78.4m}}$

$\bf{\green{\bold{ Thus, \:the \:height \:of \:building\: is\: 78.4 \:m}}}$