posted by Anonymous .
Two blocks of masses M and 3M are placed on a horizontal, frictionless surface. A light spring is attached to one of them, and the blocks are pushed together with the spring between them.
A cord initially holding the blocks together is burned; after this the block of mass 3M moves to the right with a speed of v1=2.48 m/s. What is the velocity of the block of mass M?
The force on each end of the spring is the same, the impulse is the same, the momentums are the same.