So that is what creates that centripetal acceleration and centripetal force. And so we have this other force known as the force centrifugal that basically causes it to move in the other direction. In fact, that's why this process is known as centrifugation, because it's the result of this centrifugal force. Now the next question is how exactly do we describe the rate at which different particles move inside our rotating test tube during the process of centrifugation? So in biochemistry, we describe the rate of the movement of the particles inside our test tube by using a quantity known as the sedimentation coefficient, and that is given with the lowercase S. So lowercase S is equal to the mass of that particle multiplied by one minus v bar multiplied by row divided by f. Now, in the next lecture, we're going to use physics to basically derive this equation. Now let's discuss what these quantities actually mean.