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Homework Help: Collision in two dimensions problems

  1. Oct 17, 2012 #1
    1. On a table (defining the x,y-plane laying 3 identical coins A,B and C with identical diameter of 18.00mm. The coordinates of their centers are Z(0,0), Y(60.0,0), X(60.0, 45.0) all given in mm.
    Under what angle relative to the x-axis one has to push Z against Y so that Z performs after the collision with Y another central collision with X?
    Assume elastic collision, neglect friction.

    2. m1(vi1 - vf1) = m2(vf2 - vi2)
    vi1 + vf1 = vf2 + vi2

    3. The attempt at a solution
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. I really don't understand how to find the angle when we don't have the velocities.
  2. jcsd
  3. Oct 17, 2012 #2


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    Homework Helper
    Gold Member
    2017 Award

    Hello madlin.

    Increasing the initial speed of Z would be like speeding up a video of the whole process. So, the answer will not depend on the speed.
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