Question

A projectile is fired at an angle of $ 45^{\circ} $ and reaches the highest point in its path after $ 2\sqrt2\,s $ . Find the velocity of projectile in $ m s ^{-1} $ ,

• A. $ 19.6 $
• B. $ 39.2 $
• C. $ 9.8 $
• D. $ 4.9 $

Answer 1

Answer: (B)

Given : Time taken to reach highest point,
$t=2\sqrt{2}s$
Angle of projection, $\theta=45^{\circ}$
Let $u$ be the speed of projection
$\therefore t=\frac{u\,sin\,\theta}{g}$ or $u=\frac{gt}{sin \,\theta}$
or $u=\frac{2\sqrt{2}\times9.8}{\frac{1}{\sqrt{2}}}$
$=39.2\,m\,s^{-1}$