Final answer:
The curvature of the FSP VD delta Y graph for small displacements is primarily due to the elasticity of the material, which fits the behavior depicted by Hooke's law. Fluid viscosity and frictional forces are relevant in different contexts and do not explain the graph's initial curve.
Step-by-step explanation:
The question pertains to the reason why the Force vs. Displacement (FSP VD) graph curves for a small displacement. The graph in question typically shows the deformation of an object under applied force and how the object behaves elastically for small displacements, meaning it will return to its original shape once the force is removed. Only after a certain point does the force cause permanent deformation and eventually fracture. The given options for why the graph may curve at small displacements include frictional forces, elasticity, absence of shear forces, and fluid viscosity effects.
In the context of the information provided, it is elasticity of the material that is the main factor contributing to the curvature of the FSP VD delta Y graph at small displacements. This is because the graph indicates that within the elastic region, an increase in force is proportional to an increase in length deformation, which is characteristic of Hooke's law. Therefore, elasticity is the given answer (b).
It might be tempting to consider fluid viscosity effects due to the detailed explanations about the force exerted due to viscosity, known as viscous drag, especially at varying speeds and characteristic sizes of an object moving through a fluid. However, these explanations describe phenomena that are distinct from the solid material deformation represented in the FSP VD graph. Friction is mentioned as a non-conservative force in systems with mass oscillation and spring compression and expansion, but again, the question itself is more directly related to the material's internal elasticity.