The Kid Should See This

Why do spinning rings & spinning disks have different paths?

In this silent video from Science Magazine, we can see how a spinning disk and a ring create two different paths while spinning. Try it at home. Do you see the same result? David Schultz at ScienceMag.org explains:

According to new research published in Physical Review E, the difference comes down to drag. The disk traps a layer of air between itself and the tabletop—which is key in explaining how the disk suddenly comes to a stop. But in the case of the ring, the air can escape upward through the hole. This difference in airflow causes the direction of frictional forces perpendicular to the ring’s edge to switch directions, leading to a change in the direction of its spiraling along the tabletop.

There are more spinning videos on this site, including a few that focus on the physics of it, including Rotating Saddle, Tippe Top, the Tea Twister, the Gyroscope, Euler’s Spinning Disk, and from TED Ed: What On Earth Is Spin?

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