Why are manhole covers round?

In fact, the manhole cover is round, because as long as the diameter of the cover is slightly larger than the diameter of the wellhead, no matter what the situation is, the cover will not fall into the well when it is turned upside down. So what happens if the manhole cover is made into a square or rectangle? Suppose a fast approaching car hits a manhole cover, knocking it into the air. When the lid is dropped, whether it is a rectangle or a square, it is possible to fall into the well along the diagonal of the largest scale! Since the diagonal of a square is 1.41 times the length of a side, the diagonal of a rectangle is also greater than the length of either side, and only circles have the same diameter. The round cover will not fall in anyway. Suppose that one night, a person accidentally kicked the cover up, the well was opened, and the person fell in, and the cover also fell, the person was very good, not only did he have stinky sewage under his feet, and come All of a sudden, wouldn't it make things worse!

The line segment connecting any point on the circumference to the center of the circle is called the radius. Its length is the distance between the feet of the compass when drawing a circle. When calculating the area with the same radius and side length, the area of the circle is the smallest, which saves the most material. Making the manhole cover circular is also a material saving for the country.

In addition, the hole under the cover is round. The round inspection well is more convenient for people to go down, and it is easier to dig the well. The sewer exit hole should leave enough space for one person to pass through, and one should follow the ladder. The cross-section of the person climbing down is basically round, so the circle naturally becomes the shape of the sewer manhole. Round manhole covers are just to cover round holes. In addition, the cylindrical shape is most able to withstand the pressure of the surrounding land and water.