Question

A man can throw a stone to a maximum distance of $80m$. The maximum height to which it will rise, is

• A. $30m$
• B. $20m$
• C. $10m$
• D. $40m$

Answer 1

Answer: (B)

Given , maximum horizontal range, $R_{\max }=80m$
As, range of a projectile, $R=\frac{u^2\sin 2\theta }{g}$
and it is maximum $\theta =45^{\circ }$
$\therefore \frac{u^2}{g}=80m$
Maximum height, $h=\frac{u^2{\sin }^2\theta }{2g}$
$=\frac{80}{2}\left({\sin }^{2}45^{\circ }\right)=40\times \frac{1}{2}=20m$