Question

A bullet of mass $0.1 \,kg$ is fired with a speed of $100 \,m/s.$ The mass of gun being $50 \,kg$. Then, the velocity of recoil become:

• A. 0.05 m/s
• B. 0.5 m/s
• C. 0.1 m/s
• D. 0.2 m/s

Answer 1

Answer: (D)

0.2 m/s

Answer 2

In absence of any external force, linear momentum of a system is conserved..
Linear momentum of bullet-gun system is conserved.
i.e.. Initial momentum = Final momentum
$\therefore 0=m_{1} \,v_{1}+m_{2}\, v_{2}$
or $0=0.1 \times 100+50 \times v_{2}$
$\therefore v_{2}=-\frac{10}{50}=-0.2 \,m / s$
Negative sign implies recoil.
Hence, the velocity of recoil is $0.2\, m / s$.