Why mainholes are round in the shape...?
113374
i found this explanation interesting:\n\n"circular manhole covers have the advantage that you don't have to get the corners lined up when dropping them into place."
157120
This goes along with the question of why don't we fall off the earth if it is round. The answer is because gravity is holding us (and the water) down.
943945
Round seems to be our perception of the future, and of higher technology.  Look ar all our movies, the cars are always rounder than those of today.  WE think aliens are futuristic, so I guess that means they should be round.
788730
i agree with cookie cutter\n\nwhat the heck is a round *****???
340390
Ok, since you called me out! (Actually, I'm flattered) \nMatchams appears to be a road course and perhaps the design of that road course was for the Karts to run counter-clockwise. It's just the way it's done over there. For example, why does water in toilets swirl the opposite way in the Southern Hemisphere than it does in the Northern Hemisphere? WHO KNOWS??? It just is the way it is.
890639
Skulls are not perfectly round.  http://www.infovisual.info/03/013_en.html
1158378
It seems flat to me.  However, when I peer intently  at lines of clouds over a real-long horizon I detect a curl this way and that, like it's following some sort of curvature of the surface in a distant kind of way.  It's really spooky.  But you include the question "Was it ever round?"  So if you want more on the subject, listen to Phil Hendrie on xm radio channel 152, and sometimes he has a guest General Johnson Jameson, who attempts such inquiries.  As an added bonus, a few conversations about a society of small people who live in a magical land.
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.
820312
Because air preasure is distributed evenly and in all directions. Notice that if you blow on a bubble it changes shape temporarily, but only as long as the preasure on it is from one side. After you stop blowing it returns to perfectly round.
78121
Is it round?  This is due to gravity.  Gravity pulls with equal strength in all directions; therefore any variations from a spherical shape will lead to gravitational forces that bring the shape back into that of a sphere.\n \nThis is without considering the rotation of the earth, however.  The rotation of the earth adds centrifugal effects, which cause the earth to bulge slightly at its equator and flatten slightly at its poles.  (This is like twirling a rock on the end of a string and then letting go--the rock flies away from the twirler.)  Because of these centrifugal effects, the distance from the center of the earth to the surface of the earth is about 0.33% shorter at the poles compared to the equator.
272850
it sounds like you are trying to find out about pipe connections or tubing?if this is so .you can obtain a pipefitters bluebook and it will give you all infomation on tubing and pipe and take offs and math to figure problems of different types with round pipe or tubing?i hope thats close for you.you can go to a libary and see drawings of local buildings and there are detailed.but take offs and such you have to figure.the blue book gives it all
1111034
Perhaps the link will help a little.  If you bend a pipe or metal bar, some of the metal will be in tension (stretched) and some will be in compression (squeezed).  There is a neutral plane between the two conditions that is neither stretched nor squeezed.  Often the plane passes through the centroid of the pipe (or bar).  This is easy to find if the cross-section is regular (round, square, etc.) but more difficult to find if the area is irregular or of variable properties such as density.  The centroid is similar to the center of gravity for the shape.  Hope that helps a little.
580033
You've probably seen the pictures of a grid with a giant funnel extending infinitely downward.  That's not the shape of the hole itself, but a map of the curvature of space near the singularity.  The singularity, or "hole" itself is a point of infinitely large density and infinitely small size.
496346
Tubes can have an end on them (test tubes) rounded at one end. Pipes are always open on both ends.
806436
For the same reason that water goes down the plug hole in a vortex.  Air goes from high pressure to low pressure, but it goes round areas of low pressure in ever decreasing circles.
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.
791325
Most are actually more ellipsoid in shape (i.e. not perfect spheres).\n\nI'm no astronomy/physics expeert, but I think it has something to do with gravity and rotational forces.