Question

A stone is projected with initial velocity $u$ from a building of height $h$. After some time the stone falls on the ground. Find out speed with which it strikes the ground:

• A. $\sqrt{u^2+2gh}$
• B. $\sqrt{u^3+2gh}$
• C. $\sqrt{u^2+2h}$
• D. $\sqrt{u+2gh}$

Answer 1

Answer: (A)

$\sqrt{u^2+2gh}$

Using work-energy theorem,
$W_{allforces}=\Delta K$
$W_g=\Delta K$
$mgh=\frac{1}{2}m{v}^2-\frac{1}{2}m{u}^2$
$v=\sqrt{u^2+2gh}$