4 ms·

Wouldn't the g-force direction always be the same (away from the center) regardless of direction of spin and zero at the inflection between spin directions (nor

• JohnJamesRambo 10y ago
  If you have something slung on one side of the tube, it will rapidly want to go to the other side of the tube as the centrifuge switches direction on the reverse spin.
  • Xylakant 10y ago
    If the diameter of the tube is small, the effect of changing direction is neglegtible compared to the centrifugal force.
  • Florin_Andrei 10y ago
    1. The g-force always acts in one direction: towards the outside of the disc. 2. The diameter of the tube is small. It's nearly 1-D dynamics in there. 3. Very large g-forces only happen at top rotational speeds. When not rotating, the material gets slowly mixed back up, but at the regular (i.e. very slow) diffusion speed. So: separation works always towards the outside + re-mixing is a much slower process = it works as expected.
    • JohnJamesRambo 10y ago
      Yes I understand what you are saying, that the force is going to the outside of the disc, but using even light braking (over minutes or even hours for ultracentrifuging) can disturb a pellet or separation. This is rapidly coming to a complete stop and reversing direction over and over.
      • akiselev 10y ago
        Ultracentrifuges are a whole different animal than blood centrifuges. The former are used for separating tiny things like viruses, organelles, and macromolecules while the latter are used just to separate blood into white blood cell/platelet, red blood cell, and plasma layers. These cells are orders of magnitude larger than anything you'd use an ultracentrifuge for and short of deliberatly shaking the sample, it won't mix quickly after the centrifuge.