Concept of stability. Lejeune-Dirichlet criterion. Nyquist criterion. Routh and Hurwitz criterion. Liapunov second method. Examples from rigid body dynamics. Effects of damping. Gyroscopic effects. Elastic stability under static load: Beam- columns, bars and frames, torsional buckling, buckling of rings, curved bars and arches. Dynamic instability: Divergence and flutter. Instability under nonconservative forces. Examples.