Q. A bag of mass $M$ hangs by a long thread and a bullet (mass $m$) comes horizontally with velocity $v$ and gets caught in the bag. For the combined system of bag and bullet, the correct option is
A) Momentum is $\frac{mMv}{(m + M)}$
B) Kinetic energy is $\frac{1}{1}Mv^{2}$
C) Momentum is $mv$
D) Kinetic energy is $\frac{1}{2}\frac{m^{2}v^{2}}{(M + m)}$
Explanation
(c) As ${\overrightarrow{F}}_{ext} = 0,$ hence momentum remains conserved and final momentum = initial momentum = $mv$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.