Manholes are round to prevent them from falling back into the hole. They are manufactured with an indention around the edges to allow them to fit flush with the surface. If they were square (or any shape other than round), it would be possible to lift and turn it so that it the cover fell into the hole -- both expensive to replace and very dangerous to anybody down below.
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Manhole covers are round because that is the only shape that will not fall in on itself. Having a round cover with a lip, there is no way the cover can fall or be forced into the hole it covers.
They can be any shape ! We have square and rectangular ones in my town (and there's at least a couple of triangular ones too !)
It is impossible to drop a round lid into a smaller round hole.It is because round is the only shape that if turned or flipped over, it still retains the same length across its center. If you used a square, rectangle, triangle, hexagon or any other shaped lid, it could be rotated and fall into the hole.This can't happen with the round shape.And I have worked for the phone company for the last 22 years, yes it is a pain to get a rectangular lid that weighs 100 lbs, out of a 6 foot deep hole by yourself.Two more correct answersA round cover can be moved by rolling it on its edge. A round cover contains less metal than a same-sized cover of any other shape.actually a round manhole cover isint the only shape that would work a reulux triangle would work too and square manholes would puncture tires
Yes because a sphere is round in shape
They are round in shape.They are round sacs.