First bending mode

A bending mode is one of the specific shapes a beam or bar flexes into when it vibrates at one of its natural frequencies. The first bending mode is the lowest-frequency one and usually has the simplest shape, a single bow. Free-free means the bar is not clamped at either end, which changes where the mode bends and what frequency it has.

Example: A long metal bar dropped on a hard floor rings at a low tone, and most of that tone is its first bending mode.

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