Two identical twins hold on to a rope, one at each end, on a smooth, frictionless ice surface. they skate in a circle about the center of the rope (the center of mass of the two-body system) and perpendicular to the ice. the mass of each twin is 78.0 kg. the rope of negligible mass is 4.0 m long and they move at a speed of 4.30 m/s.
(a) what is the magnitude, in kg · m2/s, of the angular momentum of the system comprised of the two twins?
· m2/s.
(b) they now pull on the rope and move closer to each other so that the rope between them is now half as long. determine the speed, in m/s, with which they move now.
/s.
(c) the two twins have to do work in order to move closer to each other. how much work, in joules, did they do?
.

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 -