An idealized cart of mass \(M\) accelerates from rest at position \(x = 0\) along a frictionless horizontal track under the action of an engine delivering a constant mechanical power \(P_0\). A student notes that because \(P_0 = Fv\), the driving force \(F(v) = P_0/v\) diverges toward infinity as the speed approaches zero at the starting point. However, when the cart reaches a displacement \(x = D\), its measured kinetic energy is finite. Which of the following provides the correct physical explanation for why the work done by the engine over the displacement \(D\) is finite?