simple harmonic motion
The simplest kind of periodic motion in an elastic material, as when a blade with a fixed end is made to vibrate or a tree or branch sways in the wind. Simple harmonic motion has a single resonant frequency which, in a cantilever like a branch, depends on the length, mass and stiffness of the material.
This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
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