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Homework Help: Two Dimensional Collisions

  1. Feb 4, 2009 #1
    1. The problem statement, all variables and given/known data

    A 5.0-gram particle moving 60 m/s collides with a 2.0-gram particle initially at rest. After the collision each of the particles has a velocity that is directed 30° from the original direction of motion of the 5.0-gram particle. What is the speed of the 2.0-gram particle after the collision?


    2. Relevant equations

    conservation of kinetic energy equation
    conservation of linear momentum equation and the x and y components

    m1v1i=m1v1fcos(theta) + m2v2fcos(phi)

    3. The attempt at a solution

    m1=5
    m2=2
    m2=.4m1

    theta=30
    phi=30

    Since the the only two variables I am missing are the two final velocities, I have tried solving one of the equations for mass2s final velocity and then subsituting that value into either the original equation or another one. Everytime i end with an answer that is not one of my choice. I am confused as to how i should go about find the final velocities.
     
  2. jcsd
  3. Feb 4, 2009 #2

    Doc Al

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    Staff: Mentor

    That's good for the x-components. What about the y-components? (That will give you the second equation needed.)
     
  4. Feb 4, 2009 #3
    0=m1v1fsin(theta)-m2v2fsin(phi) right?
     
  5. Feb 4, 2009 #4

    Doc Al

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    Staff: Mentor

    Right!
     
  6. Feb 4, 2009 #5
    Thanks a lot. That has been taunting me all day. I tried everything else but that. Yet that was so simple. Again, thank you.
     
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