Question

A ball is thrown vertically upward.It goes to a height of 20m and then return s to a ground in 4s. Taking g=10m/sec2(square), find its initial velocity, final velocity of the ball on reaching ground and total time for the journey of the ball.

Answer 1

$h = ut - \frac{1}{2} g {t}^{2}$
$20 = 4u - \frac{1}{2} \times 16g$
$u = 25 \frac{m}{s}$
projected velocity=velocity before touching the ground

$t = \sqrt{ \frac{2h}{g} }$
$t = 2$
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