A particle with restoring force proportional to displacement and resisting force proportional to velocity is subjected to a force . If the amplitude of a particle is maximum for frequency while the energy is maximum for the frequency then (where = natural frequency of oscillation of particle)
In forced vibration, amplitude of oscillation is given by
Amplitude when =0
Here = Natural frequency of oscillation
= Frequency of external periodic force.
Again, energy of oscillation A2