Work and changes in kinetic energy for system of particles

Suppose that the experiment from the discussion were repeated with a spring between blocks A and B as shown below. This time, the blocks start from rest at time to and come to rest at time to after having moved a distance d. from their initial positions. Each hand pushes with a constant force of magnitude F. A. Treat blocks A and B and the spring as a system: system ABS. Over the interval from to to t4: i. Is Wnet,ext, ABS the net work done by external forces on system ABS, positive, negative, or zero? Briefly explain. ii. Is A KABS the change in kinetic energy of system ABS, positive, negative, or zero? Briefly explain. ili. Explain how your answers are inconsistent with the relationship AK ABS = Wnet,ext, ABS. The results here hint at an incomplete model. While the work-kinetic-energy theorem applies well to single particle systems it is insufficient in modeling systems with multiple particles