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Homework Help: Impulse and Momentum: Gernade Problem

  1. Apr 5, 2009 #1
    1. The problem statement, all variables and given/known data
    A grenade of mass 10kg explodes into three pieces in the same plane, two of which, A(5.0kg) and B(2.0kg), move off as shown. Calculate the velocity of the 3.0 kg third Piece, C

    2. Relevant equations

    3. The attempt at a solution

    I do not get the right answer at all. I'm not sure where i'm going wrong.
  2. jcsd
  3. Apr 5, 2009 #2


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    Homework Helper

    Figure momentum is going to be conserved.

    Isn't it really a matter of vector addition?

    Pa = Ma*(-Va*cos30 i + Va*sin30 j)
    Pb = Mb*(...

    These added together give you -Pc don't they?
  4. Apr 5, 2009 #3
    I'm not really sure what you mean. The way I did is the way my Teacher told me to. I'm my class is tough through Video Conference so its hard to ask her. I told her I wasent getting the right answer and she said to do it exactly the way i have it. Her answer is 128.93 m/s [R82°D]
  5. Apr 5, 2009 #4


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    I was merely treating momentum as vectors and taking the components independently.

    As an alternative method, consider the momentum in x and the momentum in y, separately.

    Pax + Pbx + Pcx = 0


    Pay + Pby + Pcy = 0

    Once you have determined the components of Pc then you can use Pythagoras to give you Pc.
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