Cutting potato grids and removing door locks are also some of the trivia in life.

\”Although it is a rudimentary skill, it is a top-notch skill.\”

Written | Wu Jinyuan

In the human society we live in now, many people and things are artificially divided into threeSixty-nineEtc., this classification is deeply rooted in a certain historical period, but it has not become a consensus among people. From the ground-breaking saying 2,700 years ago that \”meat eaters are despicable\” to the modern saying \”the humble are the smartest and the noble are the stupidest\”, they all disagree with this secular view.

Due to space constraints, we do not intend to discuss too many social science issues in this article. But unfortunately, knowledge and skills are often divided into \”high-end\” and \”low-level\”. People subconsciously tend to pursue \”high-end\” knowledge and ignore \”low-level\” knowledge. In fact, all human knowledge and skills are valuable, and there is no distinction between elegance and vulgarity. I read a couplet when I was very young, and I still remember it: \”Although there is no skill at all, it is the best effort\”. This couplet is about a barber, but if you think about it, it seems like it should be true for all three hundred and sixty lines.

It is difficult for us to change social concepts, and children grow up very quickly, so we cannot wait for social concepts to change. Therefore, I can only suggest that readers should consciously pay attention to knowledge that is mistakenly regarded as \”low-level\” by secular concepts when educating children. BecauseThis knowledge is a window for us to understand the world. It is obviously unwise to artificially close such a part of the window without any reason.

Can these \”low-level\” knowledge help children achieve good test scores? Some parents will ask this. Of course, we will talk about an example later.

The \”cold knowledge\” of steel tape measures

In a chat on a certain day of a certain year, a certain professor said impassionedly: What kind of high-tech is China doing? Even the high-end products are not good. He said and took out a steel tape measure from the tool cabinet: \”Look, what quality is this? It\’s an export product. The head is all loose.\”

Yu Weiweiyan, Nuonuoyan: Do you really not know that the head of a steel tape measure should be loose?

Of course, the metal hook at the top of the steel tape measure is specially designed to be loose, which is probably a bit of trivia. I learned it from my mentor when I was a PhD student. The instructor knew about it from his father, who was a bricklayer.

Why should the head of the steel tape measure be designed to be loose? Because the steel tape measure has two measurement modes.

Sometimes, we need to hook the steel tape measure on a reference edge to measure the length, as shown in the picture above.

Sometimes it is necessary to measure against the datum plane, as shown in the figure above.

The metal sheet used for the hook has a certain thickness. If the hook is fixed to the steel sheet of the ruler body, this thickness will cause errors. The thickness error can be compensated by designing the two rivet holes on the metal hook to be oblong so that the metal hook can loosen within a given range.

The steel tape measure should be the most adaptable modernAs the originator and prototype of the Ying system, we can now appreciate the ingenuity and originality of the unknown designer back then.

I hope every parent will tell their children about the steel tape measure. This is better than the so-called \”Edison saved his mother\” story, because it is real and can be seen. You can find interactive encyclopedias on the Internet, and Baidu has introduced this knowledge.

Excellent side dish in high-end restaurants

Also potatoes, cut open and fried. If it is cut into square strips and fried like in some fast food restaurants, it is called junk food. But if cut into corrugated hollows, it becomes an exquisite side dish in high-end restaurants.

It’s no wonder that when cut like this, it can fully come into contact with the hot oil, and the oil can freely flow back and forth, making the fried potato chips naturally more fragrant. , more crispy and delicious. However, don’t just stop eating, think about it, how did you cut it into this shape?

Of course, you will think that for a chef who can carve radish flowers, carving this shape is not a problem at all. However, if it were really carved, the cost would be sky-high. In that case, I\’m afraid people will not use potato chips as a side dish for steak, but will use steak as a side dish for potato chips. You may think of using a machine to slice slices, so what should this machine be designed like?

In fact, you don’t even need a machine, just a chip grater with a corrugated blade, you can cut such potato chips. First, use half a potato and rub out the first slice on the bottom. This first potato chip is not needed.

At this time, high and low ripples appear on the bottom of the potato, as shown in the picture below.

Rotate the potato 90 degrees around the vertical axis, as shown in the figure below. In this way, the ripples on the bottom of the potato also rotate 90 degrees.

Use this position to rub out the second potato chip on the bottom of the potato, as shown in the picture below.

At this time, the wiped-out potato chips have ripples on both sides, and the ripples on both sides are perpendicular to each other. The highest point of the bottom ripple is higher than the lowest point of the upper ripple, so potato chip surface Grid-like hollow spots will appear.

Continue to turn the potato and rub the slices, and you can easily get a lot of hollow corrugated potato chips.

We will take the trouble to explain how to make this kind of potato chips. Potato Chips, I hope readers can understand the intelligence shown in this. Cooking skills may not be useful to everyone, but intelligence. The more, the better.

Removing door locks and disassembling computers

In the industrial field, the cleverness and wisdom of engineering designers are usually not written in articles. Published, but condensed in products. Therefore, being able to absorb wisdom from various products is an important window for learning from predecessors.This kind of learning.The most direct way is to take things apart and look at them.

One thing I often encourage students to take apart is door locks. In fact, I myself sometimes take apart door locks to study them.

There is no doubt that door locks should be classified as low-tech products. After all, most door locks do not use electricity. However, there are actually a lot of things to pay attention to in door locks.

There are doors with door handles on the left and some on the right. The door can open inward or outward. A door lock should be designed to accommodate all these situations. The thickness of different doors can vary greatly, and the door lock needs to be designed to be installed on doors of different thicknesses. In addition, when closing the door, the user should be able to close the door without turning the door handle, which requires that the beveled deadbolt can be pressed in, even when the door lock is in the locked state. However, after the door is closed, the beveled latch must be locked and cannot beinsertedby a piece of thin metal from the outside The top of the piece must be opened, otherwise the meaning of the lock will be lost. How these two seemingly contradictory needs are met can be seen clearly when taken apart.

Of course, another very obvious requirement is to design all bolts indoors so that the door lock cannot be disassembled from the outside.

Of course, many parents will worry that their children will not be able to put the door lock back on after removing it. Under normal circumstances, as long as you keep records during the disassembly process and take photos frequently, the disassembled parts can always be put back together without losing them. If you are really worried, you can practice with unimportant door locks between different rooms in your home. Compared with the possible troubles, the benefits from learning are quite substantial.

Another type of thing that can encourage children to disassemble is various scrapped computers. The author himself now often disassembles old computers. Electronic products are updated very quickly. Taking apart computers can help us review the development history of electronic technology.

Many materials in used computers can be recycled, such as various fans, various motors in mechanical hard drives, powerful magnets, etc.

Although old-fashioned computers are obsolete, the knowledge used to manufacture them is still valuable. The process of dismantling old computers is a good opportunity to learn from the engineering designers of the time.

Reversible plug

Contemporary people are accustomed to directional plugs and sockets. Only in the correct direction can the plug be inserted into the socket. In many cases, the directionality of plugs and sockets is. Necessary. For example, the AC power used at home can theoretically be oriented in any direction. Connected to the electrical appliance. But in fact, in order to ensure the safety of electricity, we need to connect the outer shell of the electrical appliance to the ground. In this way, there are three pins on the power plug, and the outer shell of the electrical appliance is connected to the ground. That pin is absolutely not allowed to be connected to the live wire of the power supply, so the plug needs to be designed to have a direction.

I believe readers who have used USB memory cards have experienced that the USB card cannot be inserted into the computer. If you try randomly, the direction of the USB card is the same as the direction of the computer interface. The opposite probability should be 50% for each user. Although it is inevitable, it is an unpleasant experience after all. Therefore, if non-directional plugs and sockets can be designed, it will bring great convenience to users.

Before discussing advanced electronic technology, let’s first Let’s look at a relatively simple example. The picture below shows a car taillight bulb with two sets of filaments. One set of filaments is relatively weak and is used to indicate the position of the vehicle to the driver behind. Flash signal when turning and warning when braking.

The two sets of filaments have a total of four connecting pins. These connecting pins are pulled toOn the outside, when bent on a plastic component, it becomes a plug with four pins. This plug and the socket it matches have no directionality and can be flipped and plugged in at will.

Now comes the question. As we said before, these two sets of filaments are different. How can we ensure that when we flip the bulbinto the socket, the brighter filament and the lower filament are still in contact with each other? circuits connected instead of swapping each other? In fact, readers can see the mystery just by clicking on the photo of the light bulb to enlarge it. The pins of the two sets of filaments are arranged as shown below.

Annotated in the picture A and B are the respective pins of the two sets of filaments. It is not difficult to see that if we flip this plug180 degrees, although the pins of the two sets of filaments are reversed, Still the same set of filaments in their respective places.

You may think that your child will make a lot of money in the future, so how can he learn such a trivial thing. So, let\’s take a look now at how computer companies that make a lot of money please consumers. The external plug and socket of the computer in the picture below are called USB-C plug sockets.

This kind The USB-C plug socket is a versatileThe connection standard can meet the various needs of connecting electronic products to the outside world, such as power interfaces, memory card interfaces, video interfaces and even analog or digital audio signal interfaces, etc. For ordinary users, one of its most convenient features is that it can be flipped and plugged in at will. There is no need to worry about the plugging direction being reversed or the plug being unable toInsert into the socket. How is this done?

The USB-C socket has 24 pins, and the definition of each pin is as shown below.

First, USB-C It may be used for high-power power supply, so four pairs of pins are arranged: VBUS and GND. It can be seen that no matter how it is flipped, these two sets of pins are always in their original positions. In addition, when electronic products perform high-speed data transmission, two pairs of output and input signals are required: TX1+-, TX2+- and RX1+-, RX2+-. For these two sets of signals, TX and RX are not allowed to be swapped after flipping, but the two groups 1 and 2 can be swapped. In fact, these two sets of signals are connected to the same transceiver chip, and the swap caused by the flip can be swapped back through the selection of logic circuits in the chip. In addition, the four pairs of pins in the middle of the socket are relatively slow signals. As can be seen from the picture, they are completely allowed to be swapped as long as there is certain logical support.

You may continue to say, my children will explore the mysteries of the universe in the future, what is the use of learning these practical things? IMHO, your idea is wrong. Exploring mysteries is inseparable from physics, and it is impossible to learn physics without absorbing nutrients from reality.

What nutrients have we absorbed from these soiled plugs? The answer is symmetry. Talking about symmetry, many children know about mirrors, left and right hands, this is a symmetry. The plug mentioned earlier shows another kind of symmetry, namely double rotational symmetry. Letting children know that there is more than one kind of symmetry in the world can bring an extremely valuable inspiration to them. This inspiration may be subtle, but it will undoubtedly be very important.

This two-fold rotational symmetry, in addition to its value in physics, also exists in all aspects of our lives. For example, there is a weird so-called \”imitation chess\” in Go. According to legend, Su Dongpo was the first to play it, and Zhu Yuanzhang played it to the extreme. The specific way to play is that the emperor first places a piece in the center of the chessboard (Tian Yuan), then, if the southeast is black, then the northwest is white, if the right back is black, then the left front is white (note: the ancient rule is that white goes first), all facing each other far away. Not bad. At the end of the game, only Tianyuan will win.

Of course, whether imitation chess can really win forever (apart from the difference in goals) still needs to be determined by professional Go masters. It is said that Wu Qingyuan once played imitation chess when black went first. But instead of imitating it from the beginning to the end, it stops imitating it in the middle stage and starts to change its moves.

In fact, imitation chess can be seen as a kind of rotational symmetry. If we rotate the chessboard around Tianyuan180degrees, then the situation on the chessboard is exactly the same, except that the original black and white stones Converted to each other (except for the one on Tianyuan). Therefore, we can also call the graphics on the chessboard antisymmetric graphics.

Rigid body mechanics and door springs

The mechanical principle of a rigid body rotating around a fixed axis is not complicated. This part of the content is usually for most students. They are exposed to it in the first and second grades of universitybut many students who are good at learning often learn it by themselves in high school. From a teaching point of view, this part of the content is a key point, because the thinking methods and problem-solving skills involved are so useful. At the same time, this part is another difficulty. This is because when solving practical problems, there are more factors to consider than solving the problem of particle motion, so it is easy to focus on one and lose sight of the other.

We can completely use the problems encountered by a carpenteras an intuitive reference for us to solve difficulties, and at the same time as a memory fulcrum for us to remember problem-solving skills.

When opening and closing the door of a room at home, the door handle is easy to hit the wall, which not only damages the wall, but also may damage the door handle. To do this, we need to install a door spring on the wall, as shown in the picture below.

Block the door Where should the spring be installed on the wall? If it is installed too far outside or too inside, when the door collides with the door blocking spring, it will produce a force on the door hinge. This force will cause the door to be installed. The screws of the hinge soon loosen. As shown in the figure below, (in the figure, the force marked on the door axis is the force acting on the door, and the reaction force on the hinge is equal in magnitude and opposite in direction.)

To do this, we need to install the door spring in a suitable position so that the force on the door hinge is zero.

To solve this problem, we can Treat the entire door as a rigid body. In this way, the impact force of the door spring on the door plays two roles. First, it produces a negative acceleration on the center of mass of the door, causing the movement of the center of mass of the door to stop. Second, this impact force is added to the door. A moment on the door. This moment produces a negative angular acceleration on the rigid body. , causing the door to stop rotating.

These two effects need to have a suitable ratio to achieve the two deceleration processes perfectly. If the spring is installed near the door, it provides. The torque is relatively large, which can effectively reduce the door speed. In contrast, the force required to decelerate the center of mass is not enough, and the door shaft needs to provide a part to supplement it.

On the contrary, if the spring is installed in the middle of the door, the spring needs to compare with the door. A large impact force is required to decelerate the center of mass. The door The shaft will have a reverse effect on the door panel to offset part of it. In either case, the screws on the door shaft hinge will be loosened. , we need to install the spring in a suitable position so that the two functions The ratio is appropriate without the need for additional force from the door shaft.

In order to calculate this appropriate position, we need to write three equations: one is Newton\’s second law and the other is the dynamic force of the rigid body. Equation, whose form is very similar to Newton\’s second law. The third one is for gate.The conversion relationship between angular acceleration and center of mass acceleration. In fact, all rigid body motion problems require these three relations, which is the difficulty of this type of problem. By analyzing the practical problem of door spring, we have solved the difficulty.

(Source: pixabay.com)

Sometimes, people divide knowledge into \”advanced\” and \”elementary\” according to its difficulty \”This formulation is relatively neutral compared to \”low level\”. In fact, what people usually call \”low-level\” knowledge is exactly the elementary common sense knowledge that people should learn. From this perspective, \”low-level\” knowledge and skills are a rich treasure trove of human wisdom. Compared with all kinds of advanced knowledge that are relatively difficult to learn, elementary knowledge can be said to be a rich ore that is easy to mine. Only when a person can seriously and extensively absorb all kinds of \”low-level\” knowledge can he become a truly knowledgeable person.

Source: Mr. Sai

Editor: Red Comet