# B Vocabulary: What do you call spinning on the opposite axis?

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1. Nov 19, 2016

### RabbitWho

So imagine you have two disks, and from your perspective one is spinning on its vertical axis and the other one is spinning on its horizontal axis. What do you call that?

And what would it mean to "spin at the opposite polarity" if such a sentence makes any sense at all?

Thank you! Sorry if this is the wrong place, there isn't an "inane questions" section :(

2. Nov 19, 2016

### Staff: Mentor

I would call the two axes "orthogonal" or "perpendicular."
To me, it would mean "rotate in the opposite direction, that is, clockwise versus counterclockwise, when looking along the axis from one 'end'".

3. Nov 19, 2016

### Cutter Ketch

I think I know what you mean. This question leads to a lot of careful language in science papers. Most commonly the terminology of ellipsoids is used. "minor axis" "major axis" "semimajor axis". For a disk there is the minor axis and the other two are the same, both major, and arbitrary in exactly which radial direction. Of course disks aren't ellipsoids, so other language is used. "Axial" and "radial" are common, but those aren't used to describe axes of rotation. While "radial axis" may be decipherable "axial axis" would be terrible. Sometimes "Axis of symmetry" and "perpendicular to the axis of symmetry"

In the end cylinders and disks have an axis of symmetry that we already call an axis. Describing the axis of rotation is always going to trip on that. I say stick with the ellipsoids terminology.

4. Nov 19, 2016