Answer
Minimum launch speed to complete the jump $=5.56m/s$
Work Step by Step
$S=ut+\frac{1}{2}at^{2}$
$4=0+4.9t^{2}$
$t=0.9s$
So, required horizontal speed = $\frac{5}{0.9}m/s=5.56m/s$
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