A thin uniform rod of length L, and we need the radius of gyration k about an axis passing through its centre and perpendicular to its length.Formulae:Moment of inertia (M.I.) about the given axis for a uniform rod is:I=121​ML2The radius of gyration k is related to the moment of inertia byI=Mk2Substituting:Mk2=121​ML2k2=12L2​k=12​L​