Randall D. Knight — Interactions and Potential Energy: Problem 57

A block weighing 2.6 kg is attached to a horizontal rope that exerts a variable force \( F_x = (20 - 5x) \text{ N} \), where \( x \) is in meters. The coefficient of kinetic friction between the block and the floor is 0.25. Initially, when the block is at rest, \( x = 0 \text{ m} \). What is the block’s speed when it has been pulled to \( x = 4 \text{ m} \)?