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Homework Help: Calculating Final Velocity of Two Objects

  1. Apr 26, 2013 #1
    A space vehicle travelling at a velocity of 100m/s separates by a controlled explosion into two sections of mass 850kg and 250kg. The two parts carry on in the same direction with the heavier rear section moving 120m/s slower than the lighter front section. Determine the final velocity of each section.

    I have tried to look at a way of solving this using SUVAT but there are too many unknowns to use these equations. This question is part of an assignment I have to do, I need to know if it is even possible to do these calculations with the information that I have been given. If anyone could help me that would be great, thanks.

  2. jcsd
  3. Apr 26, 2013 #2
    Use conservation of momentum

    I guess we can use the law of perfect collision in 1-dimension,

    Total mass initially be, M = 850 + 250 = 1100 kg
    Total initial momentum will be, p = 1100*100 = 110000 kg.m/s

    After the splitting, we have two masses. The velocities of heavier mass be v1and that of the lighter mass be v2.

    Total momentum after splitting will be, 850v1 + 250v2

    It is also given that heavier section moves at a speed 120 m/s slower than the lighter section. Therefore, v1 = v2 - 120

    By the law of conservation of momentum, we have initial momentum = final momentum

    110000 = 850v1 + 250v2

    Substituting v1 = v2 - 120,

    110000 = 850(v2 - 120) + 250v2
    110000 = 1100v2 - 120*850
    8000 = 1100v2
    therefore, v2 = 7.273 m/s and
    v1 = 127.273 m/s

    Hope I am correct
  4. Apr 26, 2013 #3
    Sorry.. I have used superscripts 1 and 2 instead of subscript. Pardon
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