47. Solving a chemistry problem

4. Svedberg and Nichols, when determining the equivalent radius of arsenic sulfide particles by centrifugation, found that the particles moved from a distance of 3.6 to 4.73 cm from the axis of rotation at a speed of 10920 rpm. The viscosity of the medium is 1 cps, its density is 1.002 g/cm3; the density of the dispersed phase is 3460 kg/m3. The particle radius turned out to be 74 nm. How long did it take the particles of arsenic sulfide to cover the specified distance under these conditions?