Ok, I ran across this question as I was doing my homework and I thought it looked pretty easy. I worked on it for an hour and still had no luck with getting the correct answer. Here is the full text: An elastic collision occurs between two air hockey pucks in which one puck is at rest and the other is moving with a speed of 0.1 m/s. After the collision, the puck initially in motion makes an angle of 35.00 deg with its original direction, and the struck puck moves at an angle of 55.00 deg on the other side of the original direction. What is the final speed of the first puck and second puck? (Also, mass is the same) First thing I thought was that I could use conservation of momentum and conservation of energy in x or y direction. This would give me two equations, which would allow me to solve for final velocities. I'm not going to go through the tedium of solving all the systems of equations. I'll just tell you that in the end I got V1=.0628 m/s (This is the initially stationary puck) V2=.0897 m/s Is the answer you guys get? It's not right according to my book. from equations: [tex](.1cos(35))^2=(v_1cos(55))^2+(v_2cos(35))^2[/tex] [tex]0=v_2sin(35)-v_1sin(55)[/tex] I hate when seemingly simple problems stump me and this is a great example. I normally wouldn't be surprised if it was some math error, but I spent a large amount of time diligently checking and rechecking math. The answers look legitimate. Please help?