Q. A bag of sand of mass $m$ is suspended by a rope. A bullet of mass $\frac{m}{20}$ is fired at it with a velocity $v$ and gets embedded into it. The velocity of the bag finally is
A) $\frac{v}{20} \times 21$
B) $\frac{20v}{21}$
C) $\frac{v}{20}$
D) $\frac{v}{21}$
Explanation
(d) Applying law of conservation of momentum,
$\frac{m}{20}v = \left( m + \frac{m}{20} \right)V$ or $V = \frac{v}{20} \times \frac{20}{21} = \frac{v}{21}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.