Question

An oblique projectile projected from ground takes time $4s$ to travel rom $P$ to $Q$ while takes $2s$ to travel from $S$ to $T$. Height $h$ of level $ST$ from level $PQ$ is:-

• A. $15m$
• B. $10m$
• C. $12.5m$
• D. $8.5m$

Answer 1

The correct option is A $15m$

$PQ:T=4\sec =\frac{2u\sin \theta }{g}$

$\Rightarrow u\sin \theta =\frac{4g}{2}=2g=20$

$ST:T=2\sec =\frac{2u^{\prime }\sin \theta }{g}$

$\Rightarrow u^{\prime }\sin \theta =g=10$

$H=\frac{u^2{\sin }^2\theta }{2g}=\frac{400}{2\times 10}=20m$

$h=\frac{u{}^{\prime 2}{\sin }^2\theta }{2g}=\frac{100}{2\times 10}=5m$

$\therefore \left(H-h\right)=15m$

Hence,

option $\left(A\right)$ is correct answer.