2006-12-17 16:29:29 · 8 answers · asked by confusedgurl 1 in Science & Mathematics ➔ Engineering
because it won't fall in the hole.
2006-12-17 16:33:44 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Most manhole covers are actually rectangular in th UK. It is just as easy to drop a round cover down the hole as it is a square or rectangular one, it depend on the shape of the hole, not the shape of the cover.
2006-12-18 07:57:40 · answer #2 · answered by Timbo 3 · 0⤊ 0⤋
It has often been stated falsely that the circle is the only shape that
cannot fall in the hole.
Actually, any "constant width" shape does that trick.
There are an infinite number of other constant-width shapes
besides the circle. One is the "Reuleaux Triangle"
http://mathworld.wolfram.com/ReuleauxTriangle.html
http://mathworld.wolfram.com/CurveofConstantWidth.html
Round manhole covers have other advantages, like no weak points
(due to symmetry every boundary point is the same as every other).
2006-12-18 01:00:05 · answer #3 · answered by warren_d_smith31 3 · 0⤊ 0⤋
A round cover is the only shape for which it is impossible to accidentally (or otherwise) drop the cover through the hole.
2006-12-18 00:51:18 · answer #4 · answered by Nick F 6 · 0⤊ 0⤋
They are round so that no matter which way or angle they are placed over to the hole they will not be able to fall in, whereas square and triangle can.
2006-12-18 00:46:08 · answer #5 · answered by Royston W 1 · 0⤊ 0⤋
so the cover can't fall in. If it were square all some one would have to do is turn it on it's side and drop it. Down it goes plop!
2006-12-18 00:37:48 · answer #6 · answered by Anonymous · 1⤊ 0⤋
To preven the cover from going through
2006-12-18 00:31:14 · answer #7 · answered by Renaud 3 · 1⤊ 0⤋
when it is round , it will not fall in the hole
2006-12-18 01:01:26 · answer #8 · answered by haider fouad 1 · 0⤊ 0⤋