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If there are two centrifuges spinning at the same speed but one has twice the radius of the other, the contents of which centrifuge will be forced against the outside wall the most? Or to paraphrase, does the centrifugal force get stronger or weaker the further the contents get from the axis, or does the outward force stay the same, given the speed of rotation remains constant?

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The force that acts on an object in a centrifuge is called the centripetal force, and more specifically it is the centripetal force for uniform circular motion. It's usually more convenient to work with the force per unit mass, which we call the centripetal acceleration, and as the Wikipedia article explains, this is given by:

$$ a = \omega^2 r \tag{1} $$

where $r$ is the distance to the centre and $\omega$ is the rotation speed, or more precisely the angular velocity of the rotation.

In your question you specify that the rotation speed is constant, i.e. $\omega$ is constant. In that case equation (1) tells you how the centripetal acceleration $a$ changes with the radial distance from the centre $r$. The force on an object of mass $m$ is then simply $F=ma$.

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  • $\begingroup$ I took it that the heavier the object is and the bigger the radius, then at the same number of revolutions it is pressed harder against the outer wall of the centrafuge. $\endgroup$
    – fernny500
    Jun 3, 2017 at 6:01

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