Why Are Manhole Covers Round? (on Microsoft brainteaser job interviews)

Re:Why Are Manhole Covers Round? (on Microsoft brainteaser j... by hobbs on Monday April 14, 2008 @11:27AM (#163179)

You can make a cover of any shape you want that won't fall in. It depends on how much the cover overlaps the hole. Even with a round cover, you can't have zero overlap or else the cover would fall in.

Now back to the correct answer, which is because the manholes are round - that begs the question of why manholes are round. It's probably a matter of equally distributing the sideways forces from the dirt plus a matter of being able to manufacture round tubes more easily than, say, square tubes or hexagonal tubes.

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Re:Why Are Manhole Covers Round? (on Microsoft brainteaser j... by TrevorJ on Monday April 14, 2008 @04:22PM (#163463)

Actually, no, a square cover would have to have a much wider flange in order to ensure that it could not fall in . (rotated 45 degrees in relation to the whole and tipped up, a square cover would fall in)

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Re:Why Are Manhole Covers Round? (on Microsoft brainteaser j... by hobbs on Monday April 14, 2008 @04:51PM (#163505)

Actually, yes, that's exactly what I was getting at. You'd have to make the square cover sqrt(2) times wider than the hole, but you could still prevent it from ever falling in. (Granted, it's not a very efficient solution, though.)

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Re:Why Are Manhole Covers Round? (on Microsoft brainteaser j... by TrevorJ on Tuesday April 15, 2008 @12:31AM (#163813)

Ok, agreed :-)

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Re:Why Are Manhole Covers Round? (on Microsoft brainteaser j... by Frocer on Monday April 14, 2008 @12:02PM (#163218)

It won't be a cover unless it's slightly larger than the hole wouldn't it? :)

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