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Homework Help: V of center of mass

  1. Oct 15, 2006 #1
    If a particle of mass 5.3 kg is moving east at 10 m/s and a particle of mass 19 kg is moving west at 10 m/s, what is the velocity of the center of mass of the pair?

    This one should be simple, here is my work:

    Vcm = (m1v1 + m2v2) / (m1 + m2)

    (-5.3kg*10m/s + 19kg * 10m/s) / -5.3 + 19

    = 10m/s

    This is wrong according to my book, why isn't this velocity of the center of mass correct ? Thanks again for all the help tonight everyone.
     
  2. jcsd
  3. Oct 15, 2006 #2

    OlderDan

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    A sign problem perhaps?
     
  4. Oct 15, 2006 #3
    I thought since the 5.3kg particle was moving east it would have a different sign (-). In any case, the answer is still the same with a positive sign...
     
  5. Oct 15, 2006 #4

    OlderDan

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    The velocity direction gives you a (-) for the velocity. The mass is always positive.
     
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