Why centrifuges on Earth and in space would be the same?

[Cyber]

In this forum I read a thread about centrifuge and learned that, ''There is no difference between centrifuges on Earth and centrifuges in space because gravity is in no way related to how a centrifuge works''

Reference https://www.physicsforums.com/threads/how-do-centrifuges-work.148518/

But my question is if gravity isn't related here then what IS? I mean bouyancy force is active only in gravitational field, If I drop a rock in water it won't go down without gravity. Would it?

 

[Orodruin]

It depends on what you mean by "related to". If you go to the centrifuge rest frame, i.e., a rotating frame, there will be an inertial force (the centrifugal force) that works just like gravity does - a force proportional to the mass of an object.

 

[A.T.]

But my question is if gravity isn't related here...

The Earth's gravity isn't needed, because the centrifuge creates a centrifugal force field (artificial gravity).

 

[Cyber]

Hmm...I see, so the thing is, centrifuge creates artificial gravity so no need of Earth's gravity.
But then there is another question that why centrifugal force field would create downward gravity not side-ward gravity?

 

[phinds]

Hmm...I see, so the thing is, centrifuge creates artificial gravity so no need of Earth's gravity.
But then there is another question that why centrifugal force field would create downward gravity not side-ward gravity?

Who said it would ? "downward" and "sideward" are relative. Draw what you mean.

 

[Orodruin]

Hmm...I see, so the thing is, centrifuge creates artificial gravity so no need of Earth's gravity.
But then there is another question that why centrifugal force field would create downward gravity not side-ward gravity?

This is a contradiction in terms. "Downward" by definition is the direction in which the grvitational field is pointing.

 

[Cyber]

If I take a glass of water and pour in some dirt and shake it up, let it settle, Then,

If Downward gravity (vertically downward force) applied after hour or day the dirt will settle in bottom.

If Sideward gravity (horizontally centrifugal-sideward force) applied after hour or day the dirt will settle at centrifugal-side.

So, my question was why centrifuge will settle dirt in bottom shouldn't it settle at centrifugal-side?

 

[Orodruin]

If I take a glass of water and pour in some dirt and shake it up, let it settle, Then,

If Downward gravity (vertically downward force) applied after hour or day the dirt will settle in bottom.

If Sideward gravity (horizontally centrifugal-sideward force) applied after hour or day the dirt will settle at centrifugal-side.

So, my question was why centrifuge will settle dirt it bottom shouldn't it settle at centrifugal-side?

You are artificially imposing that there is a universal direction of gravity which you define as "down". The centrifuge will settle dense substances in the direction of the centrifugal force combined with whatever external gravitational field exists. Industrial centrifuges used in applications usually allow containers to tilt (or fix containers in a tilted position) in order to counter the fact that the "down" direction changes.

 

[CWatters]

So, my question was why centrifuge will settle dirt in bottom shouldn't it settle at centrifugal-side?

The test tube holders in centrifuges are hinged or angled so the bottoms of the tubes point outwards.

http://footage.framepool.com/shotimg/qf/443389605-blood-test-centrifuge-biochemistry-biotechnology.jpg