The harmonic excitation system with one degree of freedom

Forced vibration of single degree of freedom arise when work is done on the system until the system vibrates . An example of forced vibration displacements are the foundation during an earthquake or movement caused by being balanced reciprocal components .
The following figure shows the equivalent system of forced vibration with one degree of freedom. This is a generalized coordinate system shift .

 Figure 3.1 - Forced vibration of single degree of freedom

Figure 3.2 . Free body diagram : a) the external forces that function at the system , b) the internal forces

Applying Newton 's law to diagram free system , we get a differential equation that describes the leaf spring system .

Excitation of such a system is periodic , if there is T such that :

for all t . Examples of periodic excitation is shown in Figure 3.1 . Frequency periodic excitation can be calculated using the following formula :

Single-frequency excitation has the form:

where Fo is the amplitude of excitation , omega is the frequency , phase and dogs . The frequency of excitation is independent of the size of the natural frequencies