These are "problem-solver favorites." Here, the equilibrium equations from statics are not enough to find internal forces. You must use "compatibility equations" (relationships between deformations) to solve for unknowns.
The chapter bridges the gap between theoretical material science and practical engineering design by introducing the relationship between the external load, the internal deformation, and the material properties. mechanics of materials 6th edition beer solution chapter 2
This systematic approach mirrors what a high-quality document would provide. These are "problem-solver favorites