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    Question

    An object initially at rest explodes into several

    fragments. If no external forces act during the explosion, the center of mass of the fragments will:
    A Remain at the same location where the explosion occurred (and stay at rest) Correct Answer Incorrect Answer
    B Move in the direction of the largest fragment’s motion Correct Answer Incorrect Answer
    C Move in an unpredictable path Correct Answer Incorrect Answer
    D Accelerate upward Correct Answer Incorrect Answer

    Solution

    When no external force acts on a system, the center of mass (COM) of the system obeys the law of conservation of momentum.
    In this case:

    • The object was initially at rest.
    • Hence, its initial total momentum was zero.
    • Since there are no external forces, the total momentum remains zero even after the explosion.
    Thus, the center of mass must remain at rest (or continue moving with constant velocity if it was moving initially, but here it was at rest). Even though the individual fragments move in different directions, the center of mass stays at the original position and remains at rest.

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