The diagram from the previous page is reproduced at right for your convenience. Is deltaK SB, the change in kinetic energy of system SB, positive, negative, or zero? Explain. Is deltaU SB, the change in potential energy of system SB, positive, negative, or zero? Explain. Is W net ext, SB, the net work done on system SB by external forces, posiitve, negative, or zero? In either case, explain. Consider the system B: the block alone. For each hoprizontal force acting on system B, specify whether the work done by the force is positive, negative, or zero. Explain. Is deltaKB, the change in kinetic energy of system B, positive, negative, or zero? Explain. Is deltaUB, the change in potential energy of system B, positive, negative, or zero? Explain. Is W net ext, B, the net work done on system B by external forces, positive, negative, or zero? In either case, explain.