Question

A stone is released from the top of the tower of height $20\text{m}$. Then its final velocity just before touching the ground will be

• A. $20\text{m/s}$
• B. $40\text{m/s}$
• C. $200\text{m/s}$
• D. $400\text{m/s}$

Answer 1

The correct option is A $20\text{m/s}$

Here, $h=20\text{m}$
$u=0\text{m/s}$
Taking vertically upward as positive direction for reference.
$a=-g$
using kinematic equation,
$v^2$ = $u^2+2gh$
$v^2=0+2\times 10\times 20$
$v^2=400$
$\therefore v=20\text{m/s}$