Natural Frequency

Natural frequency of the system is the frequency at which it will vibrate freely.

Since every real oscillating systems experiences some degree of damping, if no external energy is supplied, the system eventually comes to rest.

For the oscillating system to maintain a constant amplitude of oscillation, it is necessary to apply an external oscillating forces.(driving force)

Forced oscillation is motion produced when a system is acted upon by an external periodic force.

The system will oscillate with the frequency of the driving force and not with the natural frequency.

resonant frequency

Resonance occurs when the amplitude of forced vibration reaches a maximum when the driving frequency equals the natural frequency of the driven system.

  • At resonance, there is a maximum transfer of energy from the driving system into the oscillating system.

Amplitude of vibration depends on:

  • The relative values of the natural frequency of free oscillations and the frequency of the driving force.
  • The extent to which the system is damped.



Theoretically, with no damping, the amplitude of oscillation of the driven system should tend to be infinitely great when the driving frequency is equal to the natural frequency of oscillation of the oscillating system.

In practice, damping prevents oscillations from getting infinitely large.

With heavier damping, all amplitudes are found to be reduced and that of the resonant frequency is less pronounced.

The lighter the damping, the higher the amplitude of oscillation and the sharper the response.


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