Answer to Question #60999 in Mechanics | Relativity for hanhtran

Question

Block A in Fig. 1 has mass 1.00 kg, and block B has mass 3.00 kg. The blocks are forced together, compressing a spring 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 scored in the compressed spring?