PYQ NEET- Motion In A Straight Line Kinematics L-9

Question: A boy standing at the top of a tower of $20 \mathrm{~m}$ height drops a stone. Assuming $\mathrm{g}=10 \mathrm{~m} \mathrm{~s}^{-2}$, the velocity with which it hits the ground is#

A) $10.0 \mathrm{~m} / \mathrm{s}$

B) $20.0 \mathrm{~m} / \mathrm{s}$

C) $40.0 \mathrm{~m} / \mathrm{s}$

D) $5.0 \mathrm{~m} / \mathrm{s}$

Answer: $20.0 \mathrm{~m} / \mathrm{s}$#

Sol:#

We know, $v^2=u^2+2 g h$

Here $\mathrm{u}=0$ $$ \therefore v=\sqrt{2 g h}=\sqrt{2 \times 10 \times 20}=20 \mathrm{~m} / \mathrm{s} $$