The main function of the circular manhole cover is to bear the upper pressure and protect the wellhead from external damage. Therefore, the mechanical principle is the basis of the circular manhole cover. According to Newton's third law, every action has an equal reaction. When people or vehicles pass through the manhole cover, a downward force will be generated, which will be offset by the reaction force of the manhole cover.
So the manhole cover must have enough strength to bear this force.
Knowledge expansion:
A circle is a geometric figure, which refers to the area surrounded by closed curves on a plane. Unlike a square or other polygon, a circle has no definite edges or corners, only a smooth curve boundary. The center of a circle is called the center of the circle, and the straight line passing through the center of the circle and intersecting the boundary of the circle is called the diameter.
Circle is very common in nature and daily life, and has many important characteristics and applications. The following are some basic properties of a circle:
1, the area of a circle can be expressed by the formula πr? Calculation, where r is the radius of the circle.
2. The circumference of a circle can be calculated by formula 2πr, where r is the radius of the circle.
3. The central symmetry of a circle means that the circle still coincides with the original circle after rotating through the central point for a certain angle.
4. The circle is the only one in plane geometry that can keep the shape of rotation symmetry, so many geometric and physical problems involve the study of the circle.
Circle is widely used in many fields. The following are some applications of circles:
1, Engineering and Science: In mechanical engineering, the circle is one of the basic shapes of many machine parts, such as gears and bearings. In physics, circles are the basis for describing many natural phenomena, such as planetary orbits and electromagnetic spectrum.
2. Computing technology: In computer graphics, the circle is a basic shape, which can be used to construct more complex images and animations.
3. Economics: In the financial field, circles are used to describe the changes and trends of stock prices and the changes of money flow.
4. Daily life: In daily life, circles are widely used in the design of various products and tools, such as clocks, tableware and transportation.