Class 11

Physics

Mechanics

Mechanical Properties of Fluids

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 $g/cm_{3}$, viscosity of water = 0.01 poise).

Vessel is $v_{r}=360010×10_{−2} m/s$

Let r be the radius of that particle. Then

$v_{r}=92 r_{2} η(σ−ρ) g$

where $σ=4×10_{3} kg/m_{2} and η =100.01 Ns/m_{3}$

After solving, we get r = 2.0 $×10_{−6}$ m.