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    Question

    Two billiard balls each of mass 0.02 kg moving in

    opposite directions with speed 5 m s−1 collide and rebound with the same speed. What is the impulse imparted to each ball due to the other?
    A – 0.3 kg m/s Correct Answer Incorrect Answer
    B – 0.4 kg m/s Correct Answer Incorrect Answer
    C – 0.5 kg m/s Correct Answer Incorrect Answer
    D – 0.2 kg m/s Correct Answer Incorrect Answer

    Solution

    Mass of each ball = 0.02 kg Initial velocity of each ball = 5 m/s The magnitude of the initial momentum of each ball, pi = mass × velocity = 0.02 × 5 = 0.1 kg m/s After the collision, the balls change their directions of motion without changing the magnitudes of their velocity. Final momentum of each ball, pf = − 0.1 kg m/s Impulse imparted to each ball = Change in the momentum of the system = pf − pi = – 0.1 – 0.1 = – 0.2 kg m/s The negative sign indicates that the impulses imparted to the balls are opposite in direction.

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