important key points of chapter#7

Damped oscillator:

Number of forces acting on damped oscillators are two i.e;

Damping force and restoring force

Remember that both these force are written with negative sign

Damping force is non-conservative while restoring force is conservative

Forced harmonic oscillator:

Number of forces acting upon forced harmonic oscillator are three, i.e,

Damping force, restoring force and an additional force that is applied force.

Remember that this applied force is written with positive sign. It is encouraging force

This applied force is not constant. This is periodic force.

Applied force has frequency. The frequency of applied force is independent variable.

Frequency of oscillator + frequency of applied force

If Frequency of oscillator (=everybody has its own natural frequency which is unchangeable) is made equal to the frequency of applied force then resonance is produced (matching of frequency)

As a result of resonance, amplitude of oscillator becomes infinite (maximum) so  its energy becomes maximum.

Remember that the frequency of radiations in microwave oven is same as the natural frequency of fat molecules and water.