The D'Alembert System is a method used in mechanics to analyze the motion of systems in equilibrium. Named after the French mathematician Jean le Rond d'Alembert, it helps in understanding how forces and accelerations interact in dynamic systems. The system is particularly useful in solving problems involving multiple bodies and their interactions. In the D'Alembert System, the concept of virtual work is applied, allowing for the calculation of forces acting on a system without needing to directly measure them. This approach simplifies the analysis of complex mechanical systems, making it easier to predict their behavior under various conditions.