MCQ
A ball projected from ground vertically upward is at same height at time $t_1$ and $t_2$. The speed of projection of ball is [Neglect the effect of air resistance]
  • A
    $g\left[t_2-t_1\right]$
  • $\frac{g\left[t_1+t_2\right]}{2}$
  • C
    $\frac{g\left[t_2-t_1\right]}{2}$
  • D
    $g\left[t_1+t_2\right]$

Answer

Correct option: B.
$\frac{g\left[t_1+t_2\right]}{2}$
b
(b)

$t_1+t_2=$ total time of flight

$t_1+t_2=2 T$

$T=\frac{t_1+t_2}{2}$, also $T=\frac{u}{g}$

$\frac{u}{g}=\frac{t_1+t_2}{2} \Rightarrow u=\frac{1}{2} g\left(t_1+t_2\right)$

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