The mass moment of inertia of an element of mass about an axis expressed in terms of the perpendicular distance, r, from the axis is expressed as being:

not too sure thinking it will always be directed towards the centre of the earth. could be wrong not sure

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.