Static observes the effect of forces on a rigid body, ignoring any possible deformations which may occur in the process. The forces are in equilibrium. In reality, forces always produce an effect in the component, such as deformation. These effects are investigated in the science of the strength of materials. The methods applied in strength of materials serve to design components so that they cannot be deformed or destroyed by applied forces.
A simple example is a statically determinate bearing-mounted beam subjected to point loads. The reactions are determined from the conditions of equilibrium. To investigate the effect of the point loads in the beam, it is notionally split into two segments. Applying the method of sections, the internal forces and moments are plotted onto the two segments and calculated by way of conditions of equilibrium. The apparatus includes a beam mounted on two supports. The beam is cut at one point. At theat point there is a low-frictin hinge with two degrees of freedom. Two force gauges determine the internal reactions to the externally applied forces at the section. The shear force is recorded and displayed directly by a force gauge. The bending moment occurring at the section is recorded by a second force gauge acting on a fixed lever arm. This force readout, divided by 10, gives the bending moment in Nm. Adjuster nuts on the two force gauges are used to align the beam horizontally and balance out any deflection.
In evaluating the experiment it becomes clear that the shear force, as opposed to the bending moment, is mostly negligible when designing components.
