January 14, 2005
Why are manhole covers round?
This may require some thought. You take your squares, for instance. A square cover you can tip up on edge and drop through the hole on the diagonal, if you follow me. Similarly with ovals. A circular hole, however, will defy the most determined efforts in this regard. (Bear in mind that there's a lip around the inside of the manhole that the cover rests on; this effectively makes the diameter of the manhole an inch or so less than that of the cover.) This means manholes are one of the few things in the universe that are absolutely goofproof.
Posted by Ghost of a flea at January 14, 2005 06:04 AM
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