Why are manhole covers round? - Marc Chamberland
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Why are most manhole covers round? Sure it makes them easy to roll, and slide into place in any alignment. But there’s another, more compelling reason, involving a peculiar geometric property of circles and other shapes. Marc Chamberland explains curves of constant width and Barbier’s theorem.
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If a manhole cover has the shape of a curve of constant width, why can’t it fall in? You may want to explore this by cutting out a circle, a Reuleaux triangle, and a square from a paper and explore placing it through its own hole.
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Abby Abner
Lesson completed
Reuleaux Polygons with an uneven number polygons. The Reuleaux Polygons won't fall at all
raahim memon
Lesson completed
The part that is in theory most likely to fall through, must be the outer upper edge of the cover,
David Chester
David Chester
Petach Tikva, Israel
Lesson in progress
All manhole covers are also either slightly conical in their thickness or have a step in their edges with corresponding slopes or steps in their surrounding frames. The part that is in theory most likely to fall through, must be the outer upper edge of the cover, but due to the above taper or step its diameter must also be greater than the smallest size of the hole.
mick lee
Lesson completed
Because we can only make a reuleaux polygons with odd-number polygons only, those reuleaux polygons cannot fall.
