Aplank of length l and mass m hangs from an axle passing through one end. the other end is allowed to hang down so that it just brushes a workbench. you place a box of height h and mass m so that it just touches the plank when sitting on the bench. you then raise the plank up, turning around the axle, so that its movable end is a height h above the bench. you let the plank go, it pivots around the axle, and hits the ball elastically. how fast does the box move after the collision if it slides without friction?

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 -

Definitely the indoraptor