Question

Two paper screens $A$ and $B$ are separated by distance $100m$. A bullet penetrates $A$ and $B$, at points $P$ and $Q$ respectively, where $Q$ is $10cm$ below $P$. If bullet is travelling horizontally at the time of hitting $A$, the velocity of bullet at $A$ is nearly

• A. 100 m / s
• B. 200 m / s
• C. 600 m / s
• D. 700 m / s

Answer 1

Answer: (D)

$10cm\Rightarrow 10\times 10^{-2}m$
$\Rightarrow 10^{-1}\Rightarrow 0.1m$
It is a case of horizontal projectile.
So, $a_x=0,u_x=4,u_y=0,a_y=-g$
$R=100m,T=\sqrt{\frac{2H}{g}}$
$\Rightarrow$ Time of flight
$R=u_{x}T$
$100=u\sqrt{\frac{2\times 0.1}{100}}$
$\Rightarrow \frac{u\sqrt{2}}{10}=100$
$u=\frac{1000}{\sqrt{2}}=707m{s}^{-1}$