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to determine the diameter of a small spherical particle.we let it settle by gravity in air...

to determine the diameter of a small spherical particle.we let it settle by gravity in air in the field of view of a microscope,the settling velocity was 0.001 ft/s,estimate the diameter of particle?

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Answer #1

The following problem can be approached as an brownian motion problem

The random motion of a small particle (about one micron in diameter) in a fluid with the same density as the particle is called Brownian motion.

Consider a large particle (the Brownian particle) immersed in a fluid of much smaller particles (atoms).

The agitated motion of the large particle is much slower than that of the atoms and is the result of random and rapid collisions due to density fluctuations in the fluid.

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