A perfectly insulated container is filled with water at a temperature of 90oC. A marble with a temperature of 50oC and a surface area of 0.003 m2 is dropped into the water. The convection coefficient of the water is 150 W / m2 K. What is the rate of heat transfer from the water to the marble?

You get 6 for mechanical

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 -

Protons have a positive charge and, collectively, give an element its atomic number.