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    a one-tonne spacecraft which is travelling at a speed of 9500 m/s is hit by a piece of debris of mass 0.5kg travelling at right angles to it at the same speed. As a result of the impact, the debris melts into the wall of the spacecraft leaving a 12cm hole.
    Estimate the average force acting during the impact

    Here is what I attempted to do:
    F = m(v-u) / t

    Momentum of spacecraft before: 1000*9500
    Momentum of debris before: 0.5*9500

    Velocity of spacecraft after: 9495 m/s (because 1000.5/(1000*9500))
    Velocity of debris after: 13431.5 m/s

    Momentum spaceship after: 1000*9495
    Momentum debris after: 0.5*12431.5

    Change in momentum of spaceship: mv-mu = 5000
    Change in momentum of debris: -1965.75

    Total change in momentum = 3034.25

    Time: 0.12/9500

    This gives me a force of 240 MN but the answer at the back of the book is 376 MN. Where have I gone wrong?
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Updated: January 21, 2017
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