Take the tour ×  The weighing scales in my kitchen are currently
showing 0 Kg. However, there is a column of air between the
scales and the ceiling that is presumably exerting pressure on
them. If I were to place those scales in a vacuum, would those
scales show a negative weight?  share|improve this question add
comment  2 Answers  up vote 8 down vote accepted  They would
show only a very tiny negative positive weight. A typical
kitchen scale has air above and below the weighing pan, and the
pressure is very nearly the same because the thickness of the
weighing pan is millimeters and the height of the atmosphere is
a million times that. The net force of the pressure is quite
small - equal to the weight of the air it displaces, and air is
about 10^3 or 10^4 times less dense than typical solid things.
So if your pan weights a few hundred grams, the scale would read
a few tenths of a gram in a vacuum.  EDIT: When there's
atmosphere, there's a buoyant force pointing up. When we lose
atmosphere, there's more forc