Normal mode and eigenfrequency

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Discussion Overview

The discussion centers on the concepts of eigenfrequency and normal mode within the context of mechanical systems, specifically relating to the equations of motion for systems such as two masses on springs. Participants explore the definitions and relationships between these terms and their implications in understanding oscillatory behavior.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant questions the difference between eigenfrequency and normal mode, suggesting confusion over the terms as they relate to solving the secular equation for a mechanical system.
  • Another participant explains that normal modes correspond to eigenvectors and eigenfrequencies correspond to eigenvalues, providing a mathematical relationship between them.
  • This explanation includes an example involving an operator and a function, indicating that solving for the functional form yields normal modes, while the associated values represent eigenfrequencies.
  • A later reply introduces a new topic regarding transverse frequency and its relation to systems oscillating under electromagnetic radiation, indicating a potential extension of the discussion beyond the initial focus.

Areas of Agreement / Disagreement

Participants appear to agree on the mathematical relationship between normal modes and eigenfrequencies, but the introduction of transverse frequency suggests that there are additional complexities and topics that remain unresolved.

Contextual Notes

The discussion does not clarify the specific conditions under which the terms eigenfrequency and normal mode are used, nor does it address potential limitations in the definitions provided. The introduction of transverse frequency raises further questions about its relevance to the initial topic.

Who May Find This Useful

Readers interested in mechanical systems, oscillatory motion, and the mathematical foundations of normal modes and eigenfrequencies may find this discussion relevant.

kaksmet
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What is the difference between eigenfriquency and normal mode? If, for example, I solve the secular equation (from the equations of motion) for a mechanical system (say two masses on springs) to obtain the eigenvalues I thought I got the normal modes, but now I am told I get the eigenfrequencies..`?

Thanks for any help to enlighten me on this matter.

/K
 
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The normal modes are the eigenvectors, the eigenvalues are what are also known as eigenfrequencies. Example Af=wf, where A is your operator (could be differential like d/dx etc), f is a function, w is the eigenvalue/eigenfrequency. If you solve this to find the functional form of f, then you have obtained the normal modes or eigenvectors as theyre also known. For each function f you find, you will also get a value of w...f1:w1, f2:w2 etc, these values of w are the eigenfrequencies.

So for the equations for two masses on a spring, the functions that describe the motion of the masses, and their amplitudes of vibration are your normal modes . To each of these normal modes will correspond a frequency of vibration, the eigenfrequency.
 
nice explanation
 
hey

It nice explanation :-)

I hve question.. what about the Transverse frequency, which systems ossillate if some electromagnetic radiations (e.g light) shines on the material.

Best regards
Abid
 

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