Two paper screens A and B are separated by 150   m . A bullet pierces A and then B. The hole in B is 15…

The bullet exhibits horizontal projectile motion.
Displacement of bullet in vertical direction,$y=15 \mathrm{cm}=0.15 \mathrm{m}$
Displacement of bullet in horizontal direction,$x=150 \mathrm{m}$

The equation of trajectory, $y=\frac{g{x}^2}{2u^2}$

$\Rightarrow 0.15=\frac{10\times {150}^2}{2u^2}$

$\Rightarrow 2u^2=\frac{10\times {150}^2}{0.15}$

$\Rightarrow u=500\sqrt{3} {\mathrm{ms}}^{-1}$