Two blocks with masses m1 = 1.2 kg and m2 = 3.5 kg are at rest on a frictionless surface with a compressed spring between them. The spring is initially compressed by 65.0 cm and has negligible mass. When both blocks are released simultaneously and the spring has dropped to the surface, m1 is found to have a speed of 3.0 m/s. What is the speed of m2? What is the spring constant of the spring? I don't even know how to start this problem. I thought about using the momentum equation, but I'm not sure how to treat the spring.