I pull 8m of rope to lift a barrel with a weight of 300N a distance of 2m off the ground using a pulley system. Assuming there is no friction:

a) How much work did I do?

b) How much force must I have used to pull on the rope?

c) What is the Mechanical Advantage of my pulley system?

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 -

It's because 3 if it was 10 it wouldn't look right do it goes up to 4d