Question

A bullet of mass $250g$ moving with a velocity $200m/s$ is stopped within $5cm$ of the target. The average resistance offered by the target is :

• A. 40 kN
• B. 30 kN
• C. 20 kN
• D. 10 kN

Answer 1

Answer: (D)

Average resistance offered by the target to the bullet is given by Newton's second law.
From equation of motion we have
$v^2=u^2-2as$
where, $v$ is final velocity, $u$ is initial velocity, $a$ is acceleration and $s$ is displacement
Given, $u=200m/s,s=0.05m,v=0$
$\therefore O=(200{)}^2-2a\times 0.05$
$\Rightarrow a=\frac{(200{)}^2}{2\times 0.5}=4\times 10^{4}m/s^2$
Resistance offered $=F=ma$
$=0.25\times 4\times 10^4$
$=10\times 10^{3}N=10kN$