Question

A bullet of mass $20g$ has an initial speed of $1m{s}^{-1}$, just before it starts penetrating a mud wall of thickness $20cm$. if the wall offers a mean resistance of $2.5\times {10}^{-2}N$, the speed of the bullet after emerging from the other side of the wall is close to :

• A. $0.4m{s}^{-1}$
• B. $0.1m{s}^{-1}$
• C. $0.3m{s}^{-1}$
• D. $0.7m{s}^{-1}$

Answer 1

The correct option is D $0.7m{s}^{-1}$

$m=20g,u=1m/s,v=?$
$S=20\times {10}^{-2}m$
$a=\frac{-2.5\times {10}^{-2}}{20\times {10}^{-3}}m/s^2$
$v^2=u^2+2as$
$v^2=1-2\times \frac{2.5\times {10}^{-2}}{20\times {10}^{-3}}\times \frac{20}{100}$
$v=\frac{1}{\sqrt{2}}\simeq 0.7m/s$