Q. Two particles which are initially at rest, move towards each other under the action of their internal attraction. If their speeds are v and 2v at any instant, then the speed of centre of mass of the system will be
A) v
B) 2v
C) Zero
D) 1.5 v
Explanation
[Solution from source] Only internal forces act, so total momentum stays zero (it was zero initially). Hence the centre of mass stays at rest and its speed is zero, whatever the individual speeds v and 2v are. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.