A powder comprising particles of various sizes is stirred up in a vessel filled to a height of 10 cm with water. Assuming the particles to be spherical, find the size of the largest particle that will remain in suspension after 1 h (density of powder = 4 g/cm3, viscosity of water = 0.01 poise).

Question

A powder comprising particles of various sizes is stirred up in a vessel filled to a height of 10 cm with water. Assuming the particles to be spherical, find the size of the largest particle that will remain in suspension after 1 h (density of powder = 4 g/cm3, viscosity of water = 0.01 poise).

Filo · Accepted Answer

Terminal velocity of the largest particle which is just about to settle at the bottom of the
Vessel is

v_{r} = \frac{10 \times 1 0 ^{- 2}}{3600} m / s

Let r be the radius of that particle. Then

v_{r} = \frac{2}{9} r^{2} \frac{( σ - ρ )}{η} g

where

σ = 4 \times 1 0^{3} k g / m^{2} an d η = \frac{0.01}{10} N s / m^{3}

After solving, we get r = 2.0

\times 1 0^{- 6}

m.

Question Text	A powder comprising particles of various sizes is stirred up in a vessel filled to a height of 10 cm with water. Assuming the particles to be spherical, find the size of the largest particle that will remain in suspension after 1 h (density of powder = 4 $g / c m^{3}$ , viscosity of water = 0.01 poise).
Answer Type	Text solution:1
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