First slide

Average Velocity

Question

A body falls freely from a height ‘h’. Its average velocity when it reaches earth is

Moderate

A

$\large \sqrt {gh}$
B

$\sqrt {\frac{{gh}} {2}}$
C

$\sqrt {2gh}$
D

$g\sqrt h$

Solution

u = 0
v²= u² + 2gh ⇒ 0 + 2gh ⇒ $v = \sqrt {2gh}$ (OR) $h = ut + \frac{1} {2}gt^2 \Rightarrow 0.t + \frac{1} {2}gt^2 \Rightarrow t = \sqrt {\frac{{2h}} {g}}$

$< V > = \frac{{u + v}} {2} = \sqrt {\frac{{gh}} {2}}$ $=\frac{h}{t}=\frac{h}{(\sqrt\frac{2h} {g})}={\sqrt\frac{gh}{2}}$

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