Discussion on Rotational Motion

The radius of gyration, often referred to by the symbol k, is
defined by the equation I = mk^2. In this equation, I is the moment
of inertia of some object about some specified axis, m is the total
mass of the object, and k is the distance from the axis such that if
all the mass were concentrated at that distance, the moment of
inertia would be the same as for the actual object (which could have
an arbitrary distribution of mass).