Question

Form a uniform disc of radius R a circular hole of R/2 is cut out the center of the whole is at R/2 from the center of the original disc. Locate the center of mass of the resulting flat body

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).