Other than finding the intial xy coordinates and knowing gravity as a factor I am not sure where to go with this problem as the formulas I have deal with final angles and not initial. The problem follows: Two spheres of mass 1kg & 1.5Kg hang @ rest at the ends of strings that are both 1.5m long and attached at the same point on the ceiling. The lighter sphere is pulled aside so that it makes an angle of 60 degrees w/ vertical. The lighter sphere is then released and the two spheres collide elastically. When they rebound, what is the largest angle with respect to the vertical that the string holding the lighter sphere makes? Help would be greatly appreciated. Thanks.