when stuff goes round a turn the more dense material goes to a higher radius, the less dense material goes to a lower radius. That's how the separation works.
to prove it, you'll need a helium balloon, a muddy field, and an automobile.
Take a helium balloon and place it in the automobile. Then drive the automobile out to the field. Now, and here's the fun part: Accelerate and make a turn to the left. As the automobile keeps turning you'll notice that while you (as a dense object) will feel thrown to the right (higher radius), but the balloon will interestingly move to the left (lower radius). When you've made your observation, quickly accelerate while making an even harder turn to the left. If your automobile is powerful enough you'll make a donut.
I guess you don't need to make the donut, but it's fun to try.