ABSTRACT
When a system requires more than one coordinate to describe its motion, it is called a multi-degrees of freedom (DOF) system, or an N-DOF system, where N is the number of coordinates required. Thus, a 2-DOF system requires two independent coordinates to describe its motion, and it is the simplest of the N-DOF systems. This chapter deals with the determination of the natural frequencies and normal modes of the 2-DOF system. All of the fundamental concepts of the multi-DOF system can be described in terms of the 2-DOF system without becoming burdened with the algebraic difficulties of the multi-DOF system. Numerical results are easily obtained for the 2-DOF system and they provide a simple introduction to the behavior of systems of higher DOF. For systems of higher DOF, matrix methods are essential, and although they are not necessary for the 2-DOF system.
