Final answer:
The net resultant of shear forces acting vertically downward on the left part of the structure includes shear forces, frictional forces, supporting forces, and the object's weight (if significant).
Step-by-step explanation:
To determine the net resultant of shear forces acting vertically downward on the left part of the structure, we must consider all the vertical forces on that portion of the structure. First, we take into account the shear forces applied directly to the object, usually depicted in figures like F on tangential surfaces. In addition to these, we should consider any supporting forces that act to prevent rotation (although their distorting effects are typically ignored in such analyses) and are responsible for maintaining equilibrium. The question also indicates that the weight may not be as significant compared to the shear forces if the latter are large enough to cause deformations. Lastly, any frictional forces acting on interfaces between objects should also be included if they are directed vertically.
In summary, the net vertical force acting downward will be the sum of the shear forces, the vertical component of any supporting forces, frictional forces if present, and the weight of the object (if not negligible). This net force is often of interest in engineering and physics to determine the stability and potential deformation of materials under stress.