Visit for customized academic assistance in Engineering. br br Classification of Vibrations: br Vibration can be classified in several ways. Some of the important classifications are as follows. br br • Free Vibration. If a system, after an initial disturbance, is left to vibrate on its own, the ensuing vibration is known as free vibration. No external force acts on the system. The oscillation of a simple pendulum is an example of free vibration. br br • Forced Vibration. If a system is subjected to an external force (often, a repeating type of force), the resulting vibration is known as forced vibration.