What's the physical meaning of Svedberg unit?
Wikipedia:


  The sedimentation coefficient is the ratio of the speed of a substance in a centrifuge to its acceleration in comparable units. A substance with a sedimentation coefficient of 26S (26×10−13 s) will travel at 26 micrometers per second (26×10−6 m/s) under the influence of an acceleration of a million gravities (107 m/s2). Centrifugal acceleration is given as rω2; where r is the radial distance from the rotation axis and ω is the angular velocity in radians per second.


In other words, at 1x g a 1S particle will travel at 10-13 m s-1 = 0.1 pm s-1

Particles with higher values of S will travel proportionately faster, and increasing g force will also increase sedimentation rate.

Let's look at the example of a 50S ribosome at 100 000 g:

rate of sedimentation = 10-13 x 105 x 50 m per sec = 50 x 10-8 m s-1

So how long to travel 10 cm = 10-2 m?

=10-2/(50 x 1010-8) s

= approximately 5.5 h, which seems about right.