Types of Vibratory Motion

The following types of vibratory motion are important from the subject point of view:

1. Free or Natural vibrations: When no external force acts on the body, after giving it an initial displacement, then the body is said to be under Free or Natural vibrations. The frequency of the free vibrations is called Free natural frequency.

2. Forced vibrations: When the body vibrates under the influence of external force, then the body is said to be under Forced vibrations. The external force applied to the body is a periodic disturbing force created by unbalance. The vibrations have the same frequency as the applied force.

Note: When the frequency of the external force is same as that of the natural vibrations, resonance takes place.

3. Damped vibrations: When there is a reduction in amplitude over every cycle of vibration, the motion is said to be Damped vibration. This is due to the fact that a certain amount of energy possessed by the vibrating system is always dissipated in overcoming frictional resistance to the motion.