14.8 Free and Forced Oscillations
A body is said to be executing free vibrations if it oscillates with its natural frequency without the interference of an external force.
For example, a simple pendulum shown in Fig. 14.12 vibrates freely with its natural frequency that depends only upon its length when it is slightly displaced from its mean position.
(Fig 14.12: Illustration of Free oscillation of simple pendulum)
In free oscillations, the total energy of the body remains constant i.e., energy is conserved. As we are assuming in the absence of resistance force the amplitude of the oscillation remains constant.
If a freely oscillating system is subjected to an external force, then forced vibrations will take place. Such as when swing is struck repeatedly, then forced vibrations are produced as shown in Fig. 14.13.
The vibrations of a factory floor caused by the running of heavy machinery are an example of forced vibrations. Another example of forced vibration is loud music produced by sounding wooden boards of string instruments.
(Fig 14.13: Illustration of forced oscillations of a swing)
Interesting Information
lightbulb
- Guitar string
- Bell ringing
- Atomic oscillation
- Bridge vibration
- Building sway are the examples of free oscillations