So let's suppose we take our test tube and we place it inside our centrifuge and it begins to rotate in the counterclockwise direction. So basically in this direction, as shown. So this is position one. And sometime T afterwards, this is position two. Now, let's suppose this is the particle shown in blue that we are studying inside our homogeneous mixture. And so this is the particle that we basically want to discuss and we want to basically answer the following question what forces are acting on that particle?