Demos: 1E-04 Corks in the Arc
This demonstration shows how local gravity appears in an accelerated reference frame. When the curved tube is stationary, the balls float to the end of the tube, which is higher than the middle. But when the tube is spun rapidly, a pressure gradient is set up in such a way that the middle of the tube is at a lower pressure than the ends. Thus the balls float toward the middle of the tube, as if gravity were stronger at the ends than at the middle.
Directions: Be sure the balls are at the end of the tube before starting (sometimes the stick in the middle and have to be coaxed). Turn the crank and when the tube rotation reaches a certain speed, the balls start to drift toward the center. Stop the rotation and they drift back toward the ends.
Suggestions for Presentation: It would be advantageous to perform this demo along with 1E - 3, since they illustrate the same principle.
Applications: This is essentially a curved centrifuge. Discuss the centrifuge in terms of what was observed in this demo.