Question

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

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

Answer 1

Answer: (B)

$20m$

Let the body is projected with velocity $u$ and the angle of projection be $\theta$ .

Given : Time of flight $T=4$ s

$\therefore$ Time of flight $T=\frac{2usin\theta }{g}$

$⟹$ $u^2$ $si{n}^2\theta =\frac{T^2{g}^2}{4}$ .......(1)

Maximum height reached $h=\frac{u^{2}si{n}^2\theta }{2g}=\frac{\frac{T^2{g}^2}{4}}{2g}=\frac{T^{2}g}{8}$

$\therefore$ $h=\frac{4^2\times 10}{8}=20m$