Components of stresses, equations of equilibrium, principle stresses and Mohr’s diagram in three dimensions, boundary conditions, strain components, compatibility equations, stress-strain relation and the general equation of elasticity, formulation of elasticity problems, existence and uniqueness of solution, Saint-Venant’s principle, principle of super-position and reciprocal theorem, Airy’s stress function to solve two dimensional problem, stresses in thin disk and long cylinder, torsion of prismatic bars, soap film analogy, membrane analogy and elastic stability.