Question

A body is projected from the ground at an angle of $45^{\circ}$ with the horizontal. Its velocity after $2\, s$ is $20\, ms ^{-1}$. The maximum height reached by the body during its motion is ______ $m .\left(\right.$ use $g =10 \,ms ^{-2}$ )

Answer 1

$v _{ y }= v _{ x }-20$
$\sqrt{\left( u _{ x }-20\right)^{2}+ u _{ x }^{2}}=20$
$\Rightarrow 2 u _{ x }^{2}-40 u _{ x }=0$
$\therefore u _{ x }=20$