Collision in two dimensions problems

[madlin]

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

The Attempt at a Solution

Homework Statement

Homework Equations

3. I really don't understand how to find the angle when we don't have the velocities.

 

[TSny]

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.