Two people carry a heavy electric motor by placing it on a light board 1.50 m long. One person lifts at one end with a force of 410 N, and the other lifts the opposite end with a force of 710 N.
a. What is the weight of the motor?
b. Where along with the board is its center of gravity located?
c. Suppose the board is not light but weighs 200, with its center of gravity at its center, and the two people each exert the same forces as before. What is the weight of the motor in this case?
d. Where is its center of gravity located?

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 -