The "uncle" Dang Aiguo, who was still old at the age of thirty, was still doing a prank that even the fourth-grade students in elementary school would never do anymore. Seeing Zhou Yu's clothes getting wet but could only show a helpless expression, he felt very... No, he wasn't so proud.

He asked the school workers outside to wipe the water clean, and then filled the basin with only half of the water. However, this time he did not play any stupidity or make any noise. He picked up a few bamboo dragonflies with a serious expression and said to the students:

"I have said before that tools such as bamboo dragonflies that rely on spirals to generate lift can be called propellers. The reason why we use the word "pad" is because in addition to flying into the sky, it can also push the boat forward instead of the boat. A few days ago, I asked the craftsmen to try to transform a small boat that uses propellers. When the weather is warmer, you can probably go up and experience it.

The reason why propellers can play a similar role in water and air is that although the density difference between water and air is very large, they are both substances that can flow freely and have some similar physical properties. The study of the various movement characteristics of objects in this flowing substance is fluid physics. Among them, they can be subdivided into aerodynamics, fluid mechanics, etc.

Although we only have a rough understanding now and do not need to be so detailed, as the research continues to deepen, this kind of subdivision is necessary. However, this distinction is not absolute, and there will be a certain degree of intersection between the related disciplines.

Now let’s use water to experiment with the structural strength of bamboo dragonflies, so that you can understand more intuitively why I said that if the material is not up to standard, it cannot be used as a helicopter.”

After Dang Aiguo finished speaking, he walked to the side of the podium and inserted the bamboo dragonfly into the water deeply like a propeller. Then he rubbed it hard with both hands - the water in the basin was stirred violently and splashed on the other side of the podium.

"Well...you see, the water was pushed out by the bamboo dragonfly, which is the working principle of the propeller. As for the force between the blades of the bamboo dragonfly and the water, you can try to analyze it yourself. Mechanics is an important branch of physics and is also quite commonly used in life. This may be a deeper understanding of the martial arts students."

Although the experiment did not achieve the expected purpose, the Party Patriotic still remained unchanged, nodding to everyone as if he had expected it. Then, while secretly hating in his heart that the bamboo dragonfly made by a craftsman was so strong, he repeated the experiment again.

This time, the Party Patriotic Kingdom used its greatest strength, and it was like rubbing out smoke from the handle of the bamboo dragonfly, and finally rubbing its leaves and shanks. The Party Patriotic Kingdom wiped a sweat in his heart, and took out the leaves from the water with a free expression. He raised the bamboo dragonfly, which was broken down by the power of the water, and said to everyone with both hands:

"You see, the joint part of the handle and blade is relatively weak, and if it is too strong, it will disintegrate itself. If it is a propeller used in water, it will be fine, it will drift along the water or row with your hands. If it flies in the air, the propeller will suddenly disintegrate... Then you have to try whether humans can fly like birds, relying on their arms alone. But in that case, there is no need to build an airplane, hahahahahahahahahahaha!"

The Party Patriotic thought he humorously warned the students that the quality of propellers was not up to standard. Although his own laughter was the loudest in the classroom, judging from the hilarious reactions of the students under the podium, he was really good? Well, if these students were not hilarious because the Party Patriotic ended up imitating Stephen Chow, putting his hands on his hips and laughing to the sky.

No matter what it is, it would be nice if the students could listen to the class with a smile, and the "sacrifice" he made was meaningful. To be honest, in order to educate students well, the Party and the country have also changed a lot - at least half a month ago, he would definitely not be able to put down his face and play clown to amuse the students. Although others may think that he is simply a disgrace, he still feels that he may have taken another big step forward in the road to gto.

Although humans must learn past knowledge and experience in order to survive, when the need for survival is met, a very important driving force for further scientific research is personal knowledge and interests - after all, not all research can see its economic value at once. If students cannot think science is interesting from the beginning, then they will not be interested in studying more advanced knowledge.

Dang Aiguo looked at the students who were laughing back and forth, and even laughing in tears. He raised his voice and shouted loudly to the students: "Okay, after laughing, everyone will get off get out of class and rest for ten minutes. When class is in class, we will enter the next important topic - making planes. Although this is just a model plane, if you do it well, you may be able to build gliders according to this model plane in the future. Now the get out of class is over!"

When class was held again, the students' eyes were shining and they were very interested in the following aircraft manufacturing courses. Dang Paiguo was on the iron hot to explain the general structure and principles of the aircraft, as well as the aerodynamic knowledge he knew, and then began a hands-on practice process.

In fact, it is very simple to assemble, because this was originally a paper plane that was made by the Party and Patriotic in advance and confirmed to be able to fly. What he needs to do now is to install the paper plane that has been re-disassembled into parts again.

This thick cardboard used to make paper airplanes was developed by the Wan's paper workshop of the paper mill for the request of the Party Patriotic National Academy of Sciences. Although the craftsmen felt that it did not seem to be of great practical value to make these thick cardboards, and if it was used as packaging boxes or something too luxurious, the Party Patriotic National Academy of Sciences required this request, they tried to make them.

Well... Dang Aiguo didn't think about how to make money with these thick cardboards. He originally customized such a batch of materials just for teaching needs, and by the way, he allowed craftsmen to accumulate technical experience in thick cardboard. But now it seems that as long as you draw the shape of paper airplane parts on the thick cardboard, and then match it with small propellers made of light wood, long rubber bands and other non-paper parts as power sources, then can you make money with this paper airplane toy?

But that's an extracurricular matter. Dang Paiguo is still focusing on teaching. He showed the shape of the parts one by one to the students, then inserted the parts one by one, connected the inferior rubber band that could not make bowstrings and the small propeller at the front, and made the paper plane. The center of gravity of this paper plane, Party Paiguo, has specially adjusted it. After all, the propeller in front is made of wooden, which is heavier than plastic.

After assembling the plane very skillfully, Dang Aiguo said while fiddling with his fingers on the small propeller and tightened the rubber band: "If you replace this rubber band with the power machinery I mentioned before - the engine, then you can create a real aircraft. Of course, the materials must be passed first, and the technical requirements for manufacturing aircraft engines are also very high. You may not be able to see it in your lifetime."

After raising the paper plane in his hand, Dang Maiguo gently spread it, and the paper plane flew smoothly and slowly over the classroom. The students' eyes were attracted, and there was some desire in their eyes. However, they were not overly surprised. After all, the older flying props made by humans include at least bamboo dragonflies and kites.

According to legend, "Mozi was a wooden kite, and she was defeated after three years." The aircraft made by the Party Patriotic country is just another kind of kite. And in essence, the flying principle of kite is indeed very similar to that of modern aircraft: the pulling force of the rope causes it to move relative to the air, thereby obtaining upward lift.

After that, Dang Aiguo talked about the principles of gliders, wings and paragliders. These types of aircraft are more similar to kites. However, Dang Aiguo also emphasized that we should pay attention to the material problem. Whether it is the material of the skeleton or the material of the fabric, we must pass the standard, otherwise it will not be a joke if it breaks in the air.

To this end, Dang Aiguo also showed his toy parachute made with a piece of cloth with copper coins. However, even with a qualified parachute, the flight test was still a very dangerous step in the first place. Therefore, Dang Aiguo proposed a manufacturing model and wind tunnel, conducting theoretical experiments first, and then actual manufacturing.

In fact, to mention, there is another type of ancient flying props made by humans, which is the "boomerang" made by Oceanian natives. But this kind of thing has no development potential - no matter how big it is, it cannot become an airplane. Therefore, the Party Patriotic country only draws a rough shape and briefly explains the aerodynamic principles in it. It is used as an extracurricular activity to encourage interested students to try to create a perfect "boomerang" that can fly out and fly back to their hands.

During the outdoor class that afternoon, Dang Aiguo distributed the prepared materials and props to the students, asking them to draw pictures on the cardboard according to the specifications of the parts drawn by Dang Aiguo on the blackboard, and tried to make paper airplane models by themselves.

Because it was the first time I took a ruler and charcoal wrapped in paper to draw pictures, and then used the new scissors of the Party and Patriotic to clumsyly cut out the shape of the body bit by bit, and had to make minor adjustments based on the center of gravity of the assembled semi-finished products, so the finished products that everyone finally made were almost wiped out.

Among so many paper aircraft models, only a few of them were well-made and happened to adjust the center of gravity to barely fly for a while - three of them were from Diao Chan, Cai Yan and Wang Can, who had participated in the production of the model of the Party and Patriotic aircraft. Liu Bian performed very mediocre among the students, but because everyone was basically the first time to do it, he did not perform much worse than others. The Party and Patriotic Army did not care about the results, and laughed and encouraged students who were interested in the model to find him when they encountered problems after class.

After a few days, after school, Liu Bian, who was a little timid, finally hesitated to come outside the Dang Paiguo residence...

ps: What, what, in the new week, how about the recommendation for the week? Ha~ In short, thank you for your support, I am really grateful~
Chapter completed!