Problem 2.
Brass weights are used to weigh an aluminum-made sample on an analytical balance. The weighing
is ones in dry air and another time in humid air with the water vapor pressure P =2·103 Pa. The
h
total atmospheric pressure (P = 105 Pa) and the temperature (t =20° C) are the same in both cases.
What should the mass of the sample be to be able to tell the difference in the balance
readings provided their sensitivity is m = 0.1 mg ?
0
Aluminum density ρ = 2700 kg/m3, brass density ρ =.8500 kg/m3.
1 2
2