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    Question

    A bullet is fired from a rifle which recoils after

    firing. The ratio of kinetic energy of the rifle to that of the bullet is –
    A zero Correct Answer Incorrect Answer
    B one Correct Answer Incorrect Answer
    C less than one Correct Answer Incorrect Answer
    D more than one Correct Answer Incorrect Answer

    Solution

    The rifle and bullet have zero momentum and zero kinetic energy to start with. When the trigger is pulled, the bullet gains some momentum in the forward direction, but this is canceled by the rifle's backward momentum, so the total momentum is still zero. The kinetic energies of the gun and bullet are both positive scalars, however, and do not cancel.

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