The repulsive pressure between two flat surfaces interacting in a liquid medium
ID: 1843526 • Letter: T
Question
The repulsive pressure between two flat surfaces interacting in a liquid medium is given by P = Ce ^kD, where C =100 Pa and k^1 = 20 nm are constants, and where D is the separation between the surfaces (such long-range repulsive forces can arise from electrostatic or polymer-mediated interactions in liquids). Consider a large spherical colloidal particle of radius R = 1 mm interacting with a flat surface in the liquid medium via the same interaction. When the surface of the particle is at a distance Dsub0 = 10 nm from the flat surface, (i) what is the net repulsive force between the particle and the surface, and (ii) what fraction of the total force comes from surface separations greater than 2Dsub0? If the spherical particle is made of iron and is suspended in water, what will be its average equilibrium distance from the surface?
[Answers: (i) 7.6 pN; (ii) 0.61.]
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Explanation / Answer
The answer of following question is as follows.
The net repulsive force is 7.6 pN .
The fraction for total force is .612