Principle and Method of Virtual Work

The virtual work method is a powerful tool for conversely building the mechanical model. The principle of virtual work comes out as a good candidate to answering the “Cur-question” as it may be seen that, in its generalized form, it can be established for any available mechanical model. Together with the principle, the virtual work method is generalized into an operative method for mechanical modeling in the many and various geometrical circumstances encountered in practice. This chapter introduces the concepts of virtual velocities, virtual motions and virtual rate of work. The virtual rates of work by external forces, internal forces and quantities of acceleration in the system are expressed by means of continuous linear forms on the vector space of virtual motions. The chapter then considers the case of a system S, which is in the state of equilibrium in a Galilean reference frame.