Astudent, standing on a scale in an elevator at rest, sees that his weight is 997 n. as the elevator rises, the scale reads 1226 n and then returns to normal. when the elevator slows to a stop at the top floor, the scale reads 650 n and then returns to normal. determine the magnitude of the acceleration when the elevator is slowing to a stop. (no negative numbers)

The total force F on the student is given by:

F = N - mg = ma

N normal force of the scale on to the student(scale readout)
m mass of the student
g acceleration due to gravity
a acceleration of the elevator

997 = mg
650 = m(g - a)

ma = 997 - 650
a = g(997 - 650)/997 
a = 3,4

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 -