A Ritz approach, with simple polynomials as trial functions, is used t
o obtain the natural frequencies of vibration of a class of solids. Ea
ch solid is modeled by means of a segment which is described in terms
of Cartesian coordinates and is bounded by the yz, zx, and xy orthogon
al coordinate planes as well as by a fourth curved surface, which is d
efined by a polynomial expression in the coordinates x, y, and z. By e
xploiting symmetry, a number of three-dimensional solids previously co
nsidered in the open literature are treated including a sphere, a cyli
nder and a parallelepiped The versatility of the approach is then demo
nstrated by considering several solids of greater geometric complexity
including an ellipsoid, an elliptical cylinder, and a cone.