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    Mechanics Question

    A comet has broken into three pieces of masses m1, m2, m3 with velocities
    v1, v2 and v3 respectively. Find the velocity v0 of the comet before it has
    broken.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by Unoticed View Post
    A comet has broken into three pieces of masses m1, m2, m3 with velocities
    v1, v2 and v3 respectively. Find the velocity v0 of the comet before it has
    broken.
    Use conservation of linear momentum.

    RonL
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  3. #3
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    Is this just M*v0 = m1*v1 + m2*v2 + m3*v3 where M is the mass of the comet before it breaks up?
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    Quote Originally Posted by Unoticed View Post
    Is this just M*v0 = m1*v1 + m2*v2 + m3*v3 where M is the mass of the comet before it breaks up?
    Yes, but remember that this is a vector equation, so the momenta add vectorally. (ie. if this is a problem in 2D then you actually have two equations:
    M*v_{0x} = m_1*v_{1x} + m_2*v_{2x} + m_3*v_{3x}
    and
    M*v_{0y} = m_1*v_{1y} + m_2*v_{2y} + m_3*v_{3y})

    -Dan
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  5. #5
    Grand Panjandrum
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    Quote Originally Posted by Unoticed View Post
    Is this just M*v0 = m1*v1 + m2*v2 + m3*v3 where M is the mass of the comet before it breaks up?
    But the mass before braekup is equal to the sum of the masses after break up so you have:

    (m_1+m_2+m_3)\bold{v_0} = m_1 \bold{v_1} + m_2 \bold{v_2} + m_3 \bold{v_3}

    RonL
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