What principle states that the force plus the negative of the mass multiplied by the acceleration is equal to zero?

D'Alembert's principle articulates the condition of dynamic equilibrium in mechanics, stating that the sum of all forces acting on a body, combined with the inertia force (which is the negative product of mass and acceleration), equals zero. This principle effectively combines Newton's laws of motion with the concept of virtual work, leading to the conclusion that the inertial forces can be treated as additional 'real' forces in a dynamic situation.

By expressing the condition as the force plus the negative of mass times acceleration equating to zero, D'Alembert's principle facilitates the analysis of systems in motion, allowing engineers and physicists to apply methods of statics to dynamic problems. This makes it particularly powerful when dealing with complex systems where multiple forces act in different directions.

The other principles listed serve different fundamental purposes in physics. Newton's second law focuses specifically on the relationship between force, mass, and acceleration without introducing the concept of virtual work and inertial forces. The work-energy principle relates mechanical work to kinetic and potential energy changes, while conservation of momentum deals with the total momentum in isolated systems, neither directly addressing the concept of inertial forces in the same manner as D'Alembert's principle does. Thus, D'Alembert's principle is the