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Homework Help: The Linear Momentum of a System of Particles

  1. Apr 5, 2006 #1
    Hello All, I have a question that i cant seem to get.

    If someone could help me get started on part a that would be great.

    So far i have tryed using P =m1v1 and cant seem to find any other equations that would help with the problem.

    Any help is great!
    Thank You

    Problem:
    A cart with mass 390 g moving on a frictionless linear air track at an initial speed of 1.2 m/s undergoes an elastic collision with an initially stationary cart of unknown mass. After the collision, the first cart continues in its original direction at 0.57 m/s.

    (a) What is the mass of the second cart?
    grams
    (b) What is its speed after impact?
    m/s
    (c) What is the speed of the two-cart center of mass?
    m/s
     
  2. jcsd
  3. Apr 5, 2006 #2
    Elastic means kinetic energy is conserved. You have two conservation equations:
    [tex] m_1 v_{1i}= m_1v_{1f} + m_2v_{2f}[/tex] and
    [tex] m_1 v_{1i}^2 = m_1 v_{1f}^2 + m_2v_{2f}^2[/tex]
    You can use these to determine the unknowns.
     
  4. Apr 5, 2006 #3

    Astronuc

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  5. Apr 5, 2006 #4
    but how would i solve out for m2 or v2 when the equation has both in it?

    Does v2f = v1i - v1f ?

    Edit: I got it now thanks a lot !
     
    Last edited: Apr 5, 2006
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