A horizontal plank with a frictionless axis of rotation at its center has a large mass at one end and a small mass at the other end (both are the same distance from the axis). It is initially held stationary and then released from rest. As the plank rotates (and before one end hits the ground), how do the magnitude of the net torque on the plank about the axis and the magnitude of the angular velocity vary

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -