Natural Frequency vs Frequency
Frequency of an oscillation indicates how frequent an event occurs. Frequency and natural frequency are two very important concepts discussed in physics. It is vital to have a proper understanding in frequency and natural frequency in order to excel in fields such as waves and vibrations, quantum mechanics, construction engineering, mechanical engineering and various other fields. In this article, we are going to discuss what frequency and natural frequency are, their definitions, similarities, applications and finally the difference between frequency and natural frequency.
Frequency
Frequency is a concept discussed in periodic motions of objects. To understand the concept of frequency, a proper understanding of periodic motions is required. A periodic motion can be considered as any motion that repeats itself in a fixed time. A planet revolving around the sun is a periodic motion. A satellite orbiting around the earth is a periodic motion, and even the motion of a balance ball set is a periodic motion. Most of the periodic motions we encounter are circular, linear or semicircular. A periodic motion has a frequency. The frequency means how “frequent” the event occurs. For simplicity, we take frequency as the occurrences per second. Periodic motions can be either uniform or nonuniform. A uniform can have a uniform angular velocity. Functions such as amplitude modulation can have double periods. They are periodic functions encapsulated in other periodic functions. The inverse of the frequency of the periodic motion gives the time for a period. Simple harmonic motions and damped harmonic motions are also periodic motions. Thereby the frequency of a periodic motion can also be obtained using the time difference between two similar occurrences. The frequency of a simple pendulum only depends on the length of the pendulum and the gravitational acceleration for small oscillations.
Natural Frequency
Every system has a property called the natural frequency. The system will follow this frequency, when the system is provided with a small oscillation. The natural frequency of a system is very important. Events such as earthquakes and winds can do destruction on objects with the same natural frequency as the event itself. It is very important to understand and measure the natural frequency of a system in order to protect it from such natural disasters. Natural frequency is directly related with resonance. When a system (e.g. a pendulum) is given a small oscillation, it will start to swing. The frequency with which it swings is the natural frequency of the system. Now imagine a periodical external force applied to the system. The frequency of this external force does not necessarily be similar to the natural frequency of the system. This force will try to oscillate the system to the frequency of the force. This creates an uneven pattern. Some energy from the external force is absorbed by the system. Now let us consider the case where the frequencies are the same. In this case, the pendulum will freely swing with maximum energy absorbed from the external force. This is called resonance. Systems such as buildings, electronic and electrical circuits, optical systems, sound systems and even biological systems have natural frequencies. They can be in the form of impedance, oscillation,or superposition depending on the system.
What is the difference between Frequency and Natural Frequency? • Frequency is a term commonly used to describe how frequent an event occurs, whereas the natural frequency refers to a special frequency for a given dynamical system. • The frequency of a system can take any value, but the natural frequency of a given system is a specific value.

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