In the December evening meeting, Amy Vickers led us through a new exploration that was loosely inspired by last month’s meeting on some circles.
As a warm-up, Amy presented us with this question: Why might a manhole cover (or, in the gender-neutral, maintenance cover) be round? One of the central ideas that came up in the resulting discussion was that a circle won’t fall through its own hole, no matter which way you turn it. It has a constant diameter, or constant width.
It turns out that circles aren’t the only shape with this feature! Amy presented us with another shape that behaves in a similar way: the Reuleaux triangle.
After brainstorming some questions to explore, we split up into two break-out groups – group 1 planned to explore the reuleaux triangle in more detail, and group 2 planned to explore other shapes that passed the “manhole cover test.” Using Zoom’s new self-assign feature, participants were invited to choose their own group based on what they were more interested in exploring.
Amy gave us a few online tools to play with. Some people also came up with cool images just by playing around in jam board.
Check out the links below if you want to see some of the stuff we came up with, or do your own experimenting. There’s also an awesome video on how manhole covers are made – ascinating stuff! Thanks, Amy!
Online tools:
https://www.desmos.com/calculator/nwidsblzj7
https://commons.wikimedia.org/wiki/File:Reuleaux_triangle_Animation.gif
https://www.desmos.com/calculator/wmqt92vien
Jamboards:
https://jamboard.google.com/d/1vv-VmKLpBTz6yo9xQr_vLoY4GiJ5ie0jyI13ZOlogXw/edit?usp=sharing
https://jamboard.google.com/d/1zKIYRm7cSsb8xoV02ziNgqpVowxiKwluWMV0tyVypm8/edit?usp=sharing
Video on Realeaux Triangles:
https://www.youtube.com/watch?v=-eQaF6OmWKw&vl=en-US
Video on NYC Manhole Covers:
https://video.nationalgeographic.com/video/short-film-showcase/0000014e-6574-dd5e-a75f-6d74ad760000
TED animation – Why are manhole covers round?