Mode shapes of a discrete model

This demonstration shows the two mode shapes of a discrete TDOF system.

   
a) The first mode of vibration                      b) the second mode of vibration
15-11: Mode shapes of a TDOF model

Fig. 15-11 shows a two degree-of-freedom (TDOF) model that has two natural frequencies and two vibration modes. Apply initial horizontal displacements of the two masses in the same direction and then release them at the same time, the first mode of vibration is generated, Fig. 15-11a. Apply initial horizontal displacements of the two masses in opposite directions and then release them at the same time, the second mode of vibration is generated, Fig. 15-11b.