A boy standing at the top of a tower of $20 \mathrm{~m}$ height drops a stone. Assuming $g=10…
A boy standing at the top of a tower of $20 \mathrm{~m}$ height drops a stone. Assuming $g=10 \mathrm{~ms}^{-2}$, the velocity with which it hits the ground is
$20 \mathrm{~m} / \mathrm{s}$
$40 \mathrm{~m} / \mathrm{s}$
$5 \mathrm{~m} / \mathrm{s}$
$10 \mathrm{~m} / \mathrm{s}$
Solution
Given, $g=10 \mathrm{~ms}^{-2}$ and $h=20 \mathrm{~m}$
We have
$\begin{aligned}
V & =\sqrt{2 g h} \\
& =\sqrt{2 \times 10 \times 20}=\sqrt{400}=20 \mathrm{~ms}^{-1}
\end{aligned}$