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Stoke's Law air density calculation

Stokes' Law describing partial sedimentation is given by:
Rate = [(gd^2)(Δρ)]/18η
where g = 9.81 m s^-2 is gravitational acceleration. Δρ is the density difference between particles and the air, air viscosity of η = 1.67E-4 g cm^-1 s^-1 and d is the particle diameter in centimeters.

a. Calculate the weight(g) of one cubic centimeter of air at 1.0 atm and 15 degrees celsius.

b. Assume particles have a density of 2.45 g cm^-3 and are being released by a 100 m smokestack. How long does it take (s) a 25μm particle to settle to the ground?

c. It rains exactly once a week. What is the smallest particle size (μm) that can settle to the grounds before wet removal?

Solution Preview

a. Calculate the weight(g) of one cubic centimeter of air at 1.0 atm and 15 degrees celsius.

if we use the equation alluded to in: http://hypertextbook.com/facts/2000/RachelChu.shtml (Center choice) as "The density of moist air may be determined by a similar relation:
D = 1.2929 (273.13/T) [(B - 0.3783e)/760] where T is the absolute temperature; B, the barometric pressure in mm, and e the vapor pressure of the moisture in the air in mm."

Then in our circumstance D = ...

Solution Summary

Solution to problem involving sedimentation/settling rates of airborne particles as per Stoke's Law.

$2.19