How does the principle of virtual work apply to finding equilibrium in static systems within the Theory of Mechanics?

In the Theory of Mechanics, the principle of virtual work states that a system is in equilibrium if the virtual work of the external forces is zero for any virtual displacement of the system. This is especially useful in solving for static equilibrium positions without having to calculate all the forces directly.

For example, consider a simple system of levers and pulleys with various forces applied. By using the principle of virtual work, one can assume a small displacement and calculate the work done by forces. If the sum of the work is zero for any small displacements, the system is in equilibrium.

A reference for more detailed understanding can be found at: Encyclopedia Britannica