Halliday, Resnick & Walker — Kinetic Energy and Work: Problem 16

An $8.0\text{ kg}$ object is moving in the positive direction of an $x$ axis. When it passes through $x = 0$, a constant force directed along the axis begins to act on it. Figure 7.14 gives its kinetic energy $K$ versus position $x$ as it moves from $x = 0$ to $x = 5.0\text{ m}$; $K_0 = 30.0\text{ J}$. The force continues to act. What is $v$ when the object moves back through $x = -3.0\text{ m}$?