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)

$39.2$

Answer 2

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 $u=\frac{2\sqrt{2}\times9.8}{\frac{1}{\sqrt{2}}}$
$=39.2\,m\,s^{-1}$