Some trains use a system known as maglev instead of wheels. In one version of maglev, magnets inside the track act on magnets inside the train, and when the train is at full speed it never touches the ground. The magnets never touch, but the force between them can be changed by adjusting the amount of current flowing through the train’s control system. What force do these maglev trains reduce by using magnets? elastic
electrical
friction
tension

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 -