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2.Motion in Straight Line
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A body is projected vertically up with a speed $v_0$ in gravity. The average speed of the body over a time $\frac{v_0}{g}$ calculated from the instant of projection is
A
$v_0$
B
zero
C
$\frac{2v_0}{3}$
D
$\frac{v_0}{2}$
Solution
Average velocity $=0$ because net displacement of the body is zero.
Average speed $=\frac{\text { Total distance covered }}{\text { Time of flight }}$ $=\frac{2 H_{\max }}{2 u / g}$
$\Rightarrow v_{a v}=\frac{2 u^{2} / 2 g}{2 u / g} \Rightarrow v_{a v}=\frac{u}{2}$
Velocity of projection $=\mathrm{v}$ (given)
$\therefore v_{a v}=\frac{v}{2}$
Standard 11
Physics
