Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamic electrorheological effects and interparticle force between a
  pair of rotating spheres   We consider a two-particle system in which a particle is held fixed, and the
other one rotates around the axis perpendicular to the line joining the
particles centers. The rotating particle leads to a displacement of its
polarization charge on the surface. Our results show that the rotational motion
of the particles generally reduces the force between the particles. The
dependence of interparticle force on the angular velocity of rotation will be
discussed.

20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph