1. The problem statement, all variables and given/known data Two blocks of masses M and 2M are on a frictionless horizontal surface and are held in place with a compressed spring of negligible mass between them. If the blocks are then released and the block of mass 2M leaves the spring with a velocity v, the velocity of the center of mass of the blocks is A zero B -(v/2) C -(2v/3) D -(3v/2) E -2v 2. Relevant equations n/a ? 3. The attempt at a solution I do not understand how the center of mass relates to the movement of the blocks. I remember from class that if an object exploded into thousands of pieces the center of mass would still be at the original position. So I assume it is A. Zero.