1. The problem statement, all variables and given/known data Mass 1 (M1=1 kg) slides on a frictionless surface at v0=1 m/s toward a mass (M2=2 kg) with a spring bumper of force constant k = 20 N/m. The two move together at vf at the instant that the spring is compressed to its maximum x. Find the loss in kinetic energy (KEi-KEf). I truly don't know how to start this. Can I conserve momentum? Energy? Both? How do I incorporate the work done by gravity or the spring? Thanks for your help!!