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NEET 2023 · Motion of Centre of Mass

Motion of Centre of Mass question from NEET 2023

Q5NEET 2023Easy

Motion of Centre of Mass

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 3v, the speed of centre of mass is:

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Answer: (b)

Only internal (mutual) forces act, so total momentum stays at its initial value, zero.
$v_{cm} = \frac{\vec{p}_{total}}{M} = 0$ at every instant.
So the answer is (b) zero.

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