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Physics · SYSTEMS OF PARTICLES AND ROTATIONAL MOTION
हिन्दीConsider the following statements regarding the motion of the centre of mass of an isolated system of particles: (A) The internal forces between particles always cancel in pairs due to Newton's third law and cannot alter the total linear momentum of the system. (B) If the net external force on the system is zero, the centre of mass must permanently remain at rest. (C) A projectile exploding mid-air continues to have its centre of mass follow the same parabolic path until any fragment hits the ground. (D) For an unstable nucleus decaying at rest, the fragments fly apart such that the total linear momentum in the centre-of-mass frame is always zero. Which of the above statements are correct?
Correct answer · Option 1
(A), (C) and (D) only
Explanation
Statement (B) is false because if \( \vec{F}_{\text{ext}} = 0 \), the centre of mass moves with constant velocity (uniform motion in a straight line) or remains at rest. Statements (A), (C), and (D) are correct.
