Block a in fig. e8.24 has mass 1.00 kg, and block b has mass 3.00 kg. the blocks are forced together, compressing a spring s between them; then the system is released from rest on a level, frictionless surface. the spring, which has negligible mass, is not fastened to either block and drops to the surface after it has expanded. block b acquires a speed of 1.20 m> s. (a) what is the final speed of block a? (b) how much potential energy was stored in the compressed spring?