## Vibration Terminology:

Vibration terminology consists of 12 terms which are:

**Periodic Motion****Time Period****Cycle****Frequency****Amplitude****Natural Frequency****The fundamental mode of vibration****Degree of freedom****Simple harmonic motion****Damping****Resonance****Mechanical System**

**1. Periodic Motion:**

The motion which repeats itself after an equal interval of times is called Periodic motion.

**2. Time Period:**

This is defined as time to complete one cycle is called a Time period and it is normally expressed in seconds (s).

**3. Cycle:**

It is motion completed during one time period.

**4. Frequency:**

This is defined as the number of cycles describes in one second.

This SI unit is Hertz.

**5. Amplitude:**

The maximum displacement of the vibrating body from its equilibrium position.

**6. Natural frequency:**

When no external force acts on the system after giving its an initial displacement, the body vibrates.

The vibration is called as free vibration and the frequency is called Natural frequency. This is expressed in rad/sec or Hertz.

**7. The fundamental mode of vibration:**

The fundamental mode of vibration is the model having the lowest natural frequency

**8. Degree of Freedom:**

The minimum number of independent coordinates require to specify the motion of a system at any instant is known as the degree of freedom.

**9. Simple Harmonic Motion:**

The motion of the body to and fro about a fixed point is called simple harmonic motion.

**10. ****Damping:**

It is resistance to the motion of a vibrating body.

The vibration associated with the resistance is known as Damped Vibration.

**11. Resonance:**

When the frequency of external excitation is equal to the natural frequency of the vibrating body, the amplitude of vibration becomes excessively large. This concept is called resonance.

**12. Mechanical System:**

The system consists of Mass, stiffness, and damping are known as a mechanical system.