Question

A body is projected with an angle $\theta$. The maximum height reached is $h$. If the time of flight is $4s$ and $g$ is $10m/s^2$, then value of $h$ is

• A. $40m$
• B. $20m$
• C. $5m$
• D. $10m$

Answer 1

Answer: (B)

The projectile is shown below
$t=\frac{2u\sin \theta }{g}$
$\Rightarrow 4=\frac{2u\sin \theta }{g}$
Also, $v^2=u^2+2$ as
$\Rightarrow 0^2=u^2{\sin }^2\theta -2gh$
$\frac{u^2{\sin }^2\theta }{2g}=h$
From equation (ii)
$\frac{u^2\sin \theta }{g}=2$
$\Rightarrow \frac{4g^2}{2g}=h$
$h=2g$
$h=20m$