A vibrating body always moves to and from about an equilibrium position. At the instant when it is at the equilibrium position, there are no forces acting on the body. However, the body doesn’t stop because of its inertia of motion.
If the effect of forces other than the restoring force is negligible on a vibrating body, its motion is called Natural Vibration. If no force other than the restoring force acts on the body, the body can vibrate without interruption. The amplitude of this vibration remains unchanged with the passage of time.
Types of Vibration:
There are mainly five types of vibration.
- Transverse Vibration
- Longitudinal Vibration
- Damped Vibration
- Forced Vibration
- Resonant Vibration
If the particle of a vibration body vibrates at right angles to the length of the body, the vibration is called a transverse vibration.
If the particles of a vibrating body vibrate along the length of the body, it is called a longitudinal vibration.
If resistive forces act on a vibrating body in addition to the restoring force, its amplitude gradually diminishes. After some time, the body comes to rest at its position of equilibrium. This type of vibration is called damped vibration. The resistive effect is called damping.
Practically all vibrations are damped vibrations. The vibrating body works against different resistive forces. So, its energy diminishes and the amplitude gradually decreases. To maintain a steady vibration, energy from an external source is needed. If energy is supplied from an external source in such a way that the rate of supply of energy exactly balances the rate of loss of energy, then the amplitude of the body remains constant. The value of the amplitude is similar to that of the free vibration of the body. This type of vibration is called a forced vibration.
When the frequency of the applied periodic force matches the natural frequency of a vibrating body, its amplitude rapidly increases to a large value that is called resonant vibration.