This document discusses multi degree of freedom systems and vehicle dynamics. It contains the following key points: - Multi degree of freedom systems require two or more coordinates to describe motion and have multiple natural frequencies and vibration modes. Numerical analysis is required for systems with more than two degrees of freedom. - The equations of motion for these systems can be written in matrix form using mass and stiffness matrices. Assuming harmonic motion, the equations can be reduced to an eigenvalue problem. - Normal modes are obtained by finding the eigenvectors of the system from the adjacent matrix. An example is given of two rotating rotors whose amplitudes are inversely proportional based on their inertia ratios. - Flexibility matrices relate displacements to applied