1. The problem statement, all variables and given/known data A 2.0 kg ball moving with a speed of 3.0 m/s hits, elastically, an identical stationary ball as shown. If the first ball moves away with angle 30 ° to the original path, determine a. the speed of the first ball after the collision. b. the speed and direction of the second ball after the collision. 2. Relevant equations m1v1 + m2v2 = m1v1' + m2v2' 1/2m1v1^2 + 1/2m2v2^2 = 1/2m1v1'^2 + 1/2m2v2'^2 3. The attempt at a solution m1 = m2 = 2.0kg v1 = 3.0m/s v2 = 0m/s theta1 = 30 In the x direction m1v1 + m2v2 = m1v1'cos30 + m2v2'cos(theta2) (2.0)(3.0) + (2.0)(0) = (2.0)v1'cos30 + (2.0)v2'cos(theta2) masses cancel out to leave; 3.0 = v1'cos30 + v2'cos(theta2) In the y direction m1(0) + m2(0) = m1v1'sin30 + m2v2'sin(theta2) masses cancel to leave: -v1'sin30 = v2'sin(theta2) Now here is where I am getting stuck. I know that I have to somehow combine the x and y equations as well as the conservation of NRG eqn to find the three unknowns, but I am lost as to how the algebra will work out. I think I have to square them somehow to eventually get cos^2(theta2) + sin^2(theta2) = 1 to get around the unknown theta... but everytime I have tried, it doesn't work out. Please help!