Two blocks of masses m and 3m are placed on a frictionless, horizontal surface. A light spring is attached to the more massive block, and the blocks are pushed together with the spring between them as shown in the figure below. A cord initially holding the blocks together is burned; after that happens, the block of mass 3m moves to the right with a speed of V3m = 1.80 m/s. 3m m Before a m 3m After b (a) What is the velocity of the block of mass m? (Assume right is positive and left is negative.) m/s (b) Find the system's original elastic potential energy, taking m = 0.360 kg. (c) Is the original energy in the spring or in the cord? O in the spring O in the cord