1. The problem statement, all variables and given/known data 2. Relevant equations T1 + V1 = T2 + V2 T = kinetic energy V = potential energy 3. The attempt at a solution I am only confused about how to get T2. Here is how the answer key gets T2: I don't get why Va = Vb = 0. The wheels have some velocity so it doesn't make sense how they are zero. I realize that they won't rotate because there is no friction but I still think there is a velocity. I also don't get why they can assume that the rods are pinned. How are they pinned when the spring stretches from √2 to 2m in length (this is from the solution as well)?