The right-hand side of Equation 6-7 is the \(\textit{change}\) in the quantity \(\frac{1}{2}mv^2\) over the course of the displacement (the value at the end of the displacement, where the speed is \(v_f\), minus the value at the beginning where the speed is \(v_i\)). We call this quantity the kinetic energy \(K\) of the object: