Normal mode

<p>A normal mode of a <a href="/facts/Dynamical_system/782gREl5">dynamical system</a> is a pattern of motion in which all parts of the system move <a href="/facts/Sinusoidal/mD1CB09M">sinusoidally</a> with the same frequency and with a fixed phase relation.  The free motion described by the normal modes takes place at fixed frequencies.  These fixed frequencies of the normal modes of a system are known as its <a href="/facts/Natural_frequency/pqTgYguB">natural frequencies</a> or <a href="/facts/Resonance/q7VLALUz">resonant frequencies</a>.  A physical object, such as a building, bridge, or molecule, has a set of normal modes and their natural frequencies that depend on its structure, materials and boundary conditions. 
</p><p>The most general motion of a linear system is a <a href="/facts/Superposition_principle/GKGs9C92">superposition</a> of its normal modes. The modes are normal in the sense that they can move independently, that is to say that an excitation of one mode will never cause motion of a different mode. In mathematical terms, normal modes are <a href="/facts/Orthogonality/JVIjYPog">orthogonal</a> to each other.
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Normal mode open-in-new

Normal mode