Q. A boy standing at the top of a tower of $20\ m$ height drops a stone. Assuming $g = 10\ ms^{- 2}$, the velocity with which it hits the ground is
A) $5.0\ m/s$
B) $10.0\ m/s$
C) $20.0\ m/s$
D) $40.0\ m/s$
Explanation
(c) $v = \sqrt{2gh} = \sqrt{2 \times 10 \times 20} = 20m/s$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.