__Problem - 1__

Two particles A&B are released in air at the same time, what is the ratio of settling velocity of particle A to that of particle B if the diameter of particle A is 5 µ, and for particle B is 1 µ, if they have the same density.

__Problem - 2__

A spherical particle with specific gravity 4 is settling in air, calculate the terminal settling velocity for those cases:

i) Diameter of particles = 1 µ.

ii) Diameter of particles =0.005 µ.

iii) Diameter of particles =200 µ.

__Problem - 3__

A particle is a hollow sphere of a metal oxide. The density of the metal oxide is 2000 kg/m3. The hollow portion in the center of the sphere is full of air that has the same density as the surrounding air through which the sphere is falling at its terminal velocity. The outside diameter of the sphere is 10 m and the thickness of its walls is 0.1 m (i.e., the bubble in the center has a diameter of 9.8m). How fast is it falling?

__Problem - 4__

Compute the terminal settling velocity in air of a sphere with diameter 1 µ. A spherical particle with diameter 200 µ is falling in air. If Stokes were correct for this particle, how fast would it be falling, and what would its Reynolds number be?

__Problem - 5__

It was shown that roughly one third of the surface area of the particles in a typical atmosphere is contained in particles with diameter centered about 0.02 µ, another one third in particles with diameter centered about 0.3 µ and the last one third in particles with diameters centered about 10 µ. Assume that all the particles in the atmosphere are exactly either 0.02, 0.3 or 10 µ in diameter. Calculate:

i) What would the fraction by weight be for each of the three particle sizes?

ii) What would the fraction by number be for each of the three particle sizes?

__Problem - 6__

A 0.01 µ diameter spherical particle with specific gravity 2.0 is ejected from an exhaust pipe into standard air at a velocity of 10 m/s. Calculate the travel distance before it is stopped by viscous friction? If we ignore the effect of gravity.