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Question
A nonzero external force acts on a system of particles. The velocity and the acceleration of the centre of mass are found to be v0 and a0 at instant t. It is possible that
(a) v0 = 0, a0 = 0
(b) v0 = 0, a0 ≠ 0
(c) v0 ≠ 0, a0 = 0
(d) v0 ≠ 0, a0 ≠ 0
Solution
(b) v0 = 0, a0 ≠ 0
(d) v0 ≠ 0, a0 ≠ 0
If a non-zero external force acts on a system of particles, it causes the centre of mass of the system to accelerate with acceleration a0 at any instant t. In such a case, the velocity of centre of mass of the system of particles is either v0 or zero.
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