why do you think a manhole is round?
372254
So the manhole cover can't be accidentally dropped into the hole.  If it were square or rectangular then the cover could be turned at an angle and dropped into the hole.  Would you appreciate your coworker doing that while you are crawling around fixing some power cable?  A round cover is also much simpler for the workers to roll out of the way once they have removed it from the hole.\n\nPS.  An equilateral triangle is a shape that cannot fall down into the hole if it has a small lip around it similar to a round manhole cover, but this shape is much more likely to have the corners pop up when a vehicle runs over it and is much more difficult to roll.
68065
It's due to the rotation of the Earth - specifically the Coriolis Effect. See http://answers.yahoo.com/search/search_result?p=Coriolis+Effect\n\nMy answer assumes you have a circular toilet which drains right down the middle and recieves no directional impulse from the water flowing in ;-). ie. Under strict controlled conditions, you can make water spin in opposite directions as it drains through a hole.
524282
There are two possible reasons:\n1. A non-round object has higher surface area than a round object for same volume. This in turn could lead to higher reaction rates in portions that are not round (projections etc), finally leading to the element appearing round.\n2. The surface tension of water and buoyancy keep the element on the surface at the cost of local depression in the surface of water. Surface tension tends to make the depression round, which could make the element appear round.
457528
It is not just round or oval. It is elliptical. One side is close to the sun and one side is closer to the Oort Cloud, or Kuiper Belt, or maybe the heliosphere, the end of the sun's influence to the galaxy.
91665
Its more of an elispse, not perfectly round due to the gravitational pull of the oceans by the moon and due to mountains.
1069004
For the most part, the atmosphere moves along with the surface of the earth. On the other hand, winds going in any direction tend to grind down mountain peaks.\n\nHowever, if the Earth were not fairly close to round, then the molten lava inside the earth would rupture the crust and deform the earth into a round shape. The main reason the Earth is round is gravity, not wind.
657115
A circle is the strongest shape in the world. Thats why most bridged and tunnels have arc shaped ceilings. Eggs are not perfect ovals. one side is a wider angle than the other. This is to prevent the eggs from rolling off the nest or burrow or whatever.
406527
b/c it's kinda dug into the ground...
349292
They are round because that shape can withstand the most amount of pressure without exploding/collapsing. The shape is also called a pressure vessel.
855104
so that the manhole cover won't fall into the manhole. if it was square, then it could fall into the hole when placed diagonally. same goes for any other shape.
143766
Simple!  A manhole is round so that the cover can never fall in.  If it were any other shape, like a square, rectangle or oval, you could take the cover out, flip it sideways and drop it in, but with a round hole and a round cover, it will always be just a little too big.\n\nPart 2:  I would still call it a hole if it was square.  Why wouldn't you?  Plenty of holes aren't round.  Button holes are very narrow compared to their length.  And I guess the Indian Government aren't concerned with people dropping manhole covers into a sewer, or didn't think about it.
1175270
The earth is round due to its rotation and gravity.  The sphere is a perfect structure.  Think about it, the bubble forms a skin and holds its shape.  Hurricanes are circular, so are whirpools, dustdevils, tornados.
77085
Because it is refracting light that is coming from all around. When you see a rainbow produced by a prism it looks straight but if you were able to enlarge it enough it would be round.
285187
The are round, in short, because it takes the least enegry to do it.\n\nGravity pulls the matter that will make up the planets/sun/... together.  All the forces are pointed towards to the objects center of mass, everything is being pulled inward toward the center.  With everything trying to get as close as possible to the same center of mass, the object develops a round/sphereical shape.  This shape minimizes the amount of potential energy the matter has above the center of mass.\n\nThe reason why some objects (like the Earth for example) as not totally sphereical is because they are roating around an axis.  Since the Earth is rotating on its axis (causing our days and nights), there is a bulge around the equator as the matter located there is rotating faster [tangential speed] than the matter located at the poles.  This faster tangential speed requires more centripetal force [not to be confused with the fictional "centrifugal" force] or order to keep it rotating.  In order to lessen the required force, the matter bulges out a little bid, increasing its radius away from the axis.\nCentripetal force = m(v^2/r),\nyou can see that a larger radius (r) away from the center means a smaller centripetal force is needed.
378133
well honestle I am preety sure not every mans penis is straight because i work in urology and believe me I have seen lots and lots of penis and believe me there is no way a penis can be completely straight because the curve is natural because of human nature and believe me I have seen some curvy fucked up dicks and believe me I bet yours is completely straight compared to the one's I have seen lol so seriously dont worry about it ok
1070746
It has something to do with a mysterious underlying mathematical principle. Generally, functions are curved. Laws of nature obey simple mathematical formulas. When averaged together, round shapes are formed.
1163482
1 ) It is easy to roll and move from place as it is too heavy to lift.\n\n2 ) The main reason is that it wont enter the man hole. If it is aquare it will enter the man hole easily.