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

Figure 7.26 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 \( h = 1.20 \text{ m} \), so the cart slides from \( x_1 = 3.00 \text{ m} \) to \( x_2 = 1.00 \text{ m} \). During the move, the tension in the cord is a constant \( 25.0 \text{ N} \). What is the change in the kinetic energy of the cart during the move?