Question

Formula for moment of inertia and polar moment of inertia

Answer 1

An illustration of the helium atom, depicting the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case. The black bar is one angstrom (10−10 m or 100 pm).

Answer 2

Mass is nothing but a resistance to motion similarly mass moment of Inertia is resistance to rotational motion. Area is a resistance to stress developed similarly polar moment of inertia is resistance to torsional stresses developed.