And row is the density of that medium, the fluid in which that particle is moving inside our test tube. And we divide the product by F, the frictional coefficient of that particle with respect to the fluid in which that particle is in. So, the question that we want to ask ourselves in this lecture is where exactly does this equation actually come from? So we want to derive this equation. So, in biochemistry, this equation is used to describe or tell us the rate at which our object or particle sentiments inside our test tube as it rotates in a centrifuge. So let's begin by imagining our picture.