In the principle of virtual work, we imagine that we act upon the system in such a manner as to increase one of the coordinates. We ask ourselves how much work we have to do on the system in order to ...In the principle of virtual work, we imagine that we act upon the system in such a manner as to increase one of the coordinates. We ask ourselves how much work we have to do on the system in order to increase this coordinate by a small amount. If the system starts from equilibrium, this work will be very small, and, in the limit of an infinitesimally small displacement, this “virtual work” will be zero.
