Question
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]
✓
Answer
(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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