Question

A boy standing at the top of a tower, which is 20m high, drops a stone. Assume g = 10$\frac{m}{s^2}$, find the velocity with which the stone hits the ground.

• A. 10.0 m/s
• B. 20.0 m/s
• C. 40.0 m/s
• D. 5.0 m/s

Answer 1

The correct option is B

20.0 m/s

We know, $v^2=u^2+2gh$
here, u = 0
Thus, $v=\sqrt{\left(2gh\right)}$
$v=\sqrt{(2\times 10\times 20)}=\sqrt{400}\frac{m}{s}=20\frac{m}{s}$