A mass-less spring having spring constant k is placed between a block of mass m and a block of mass 3m. Primarily the blocks are at rest on the frictionless surface and they are held altogether so that the spring between them is compressed through an amount D from its equilibrium length. The blocks are then free and the spring pushes them off in the opposite directions.
Determine the speeds of the two blocks if they detach from the spring.
Deduce your answers in terms of the variables D, k and m.