Halliday, Resnick & Walker — Kinetic Energy and Work: Problem 42

42 Figure 7-34 shows a cord attached to a cart that can slide along a frictionless horizontal rail aligned along an x axis. The left end of the cord is pulled over a pulley, of negligible mass and friction and at cord height \( h = 1.25 \) m, so the cart slides from \( x_1 = 3.00 \) m to \( x_2 = 1.00 \) m. During the move, the tension in the cord is a constant \( 28.0 \) N. What is the change in the kinetic energy of the cart during the move?