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Question: Answered & Verified by Expert
Two particles $A$ and $B$ initially at rest, move towards each other under mutual force of attraction. At an instance when the speed of $A$ is $v$ and speed of $B$ is $3 v$, the speed of centre of mass is
PhysicsCenter of Mass Momentum and CollisionNEETNEET 2023 (Manipur)
Options:
  • A $v$
  • B $4 v$
  • C $2 v$
  • D Zero
Solution:
1425 Upvotes Verified Answer
The correct answer is: Zero
Only internal force is acting on the system. Therefore $\vec{F}_{\text {ext }}=0$. It is also given that the initial velocity of COM is zero, therefore it will remain at rest.

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