There are three main types of oscillations.
(i) Free oscillations When a body vibrates with its own natural frequency, it is said to execute free oscillations. The frequency of oscillations depends on the inertial factor and spring factor, which is given by,
n = 1/2π √(k/m)
Examples: (i) Vibrations of tuning fork
(ii) Vibrations in a stretched string
(iii) Oscillations of simple pendulum
(iv) Air blown gently across the mouth of a bottle.
(ii) Damped oscillations: Most of the oscillations in air or in any medium are damped. When an oscillation occurs, some kind of damping force may arise due to friction or air resistance offered by the medium. So, a part of the energy is dissipated in overcoming the resistive force. Consequently, the amplitude of oscillation decreases with time and finally becomes zero. Such oscillations are called damped oscillations (Figure).
(i) The oscillations of a pendulum
(ii) Electromagnetic damping in galvanometer (oscillations of a coil in galvanometer)
(iii) Electromagnetic oscillations in tank circuit
(iii) Maintained oscillations: The amplitude of an oscillating system can be made constant by feeding some energy to the system. If energy is fed to the system to compensate the energy it has lost, the amplitude will be a constant. Such oscillations are called maintained oscillations (Figure).
Example: A swing to which energy is fed continuously to maintain amplitude of oscillation.