radius of gyration

physics

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July 13, 2026

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The radius of gyration is a concept in physics used to describe the distribution of mass in a rotating body. It is defined as the distance from the axis of rotation at which, if the entire mass of the body were concentrated, the moment of inertia and rotational kinetic energy would remain unchanged.1

Mathematically, the radius of gyration (k) is calculated as the square root of the moment of inertia (I) divided by the mass (m) of the body: ( k = \sqrt{\frac{I}{m}} ). The moment of inertia itself is a measure of an object's resistance to changes in its rotational speed. It depends on how the mass is distributed relative to the axis of rotation.12

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mechanics
Rotation about a moving axis
… is a distance called the radius of gyration. Comparison to equation (79) shows that k is a measure of how far from the centre of mass the mass of the body is concentrated. Using equations (87) and (88) in equation (86), one finds that
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… is a distance called the radius of gyration. Comparison to equation (79) shows that k is a measure of how far from the centre of mass the mass of the body is concentrated. Using equations (87) and (88) in equation (86), one finds that
Read More