Jeff is part of a trekking team. As he climbs a hill, he drops his water bottle, which has a mass of 0.25 kilograms. The bottle slides down the hill and is moving at a velocity of 14 meters/second the instant it hits the ground. The vertical height from where Jeff dropped the bottle is
meters. Ignore friction, and use , PE = m × g × h, and g = 9.8 m/s2.

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 -