Li Zhen opened the textbook he had prepared, glanced at it twice, and wrote two words on the blackboard.
'air resistance'
Seeing these four words, everyone licked their lips excitedly and nervously, staring at Li Zhen.
"Air resistance. Who can tell me what air resistance is?"
Xiao Shengnai raised his hand and stood up: "Master Li, when you were teaching fluid mechanics, you once talked about resistance. So if you think about it in reverse, air resistance is similar to the resistance in fluid mechanics?"
Li Zhen asked him to sit down and said, "To be more detailed, air resistance refers to the resistance of air to moving objects, which is caused by the elastic force of the air on moving objects. When an object moves forward, due to the compression of the air in front, The friction between the surfaces on both sides and the air, as well as the space behind the tail becoming a partial vacuum, are the drag caused by these effects. When running against the wind, the wind force must also be added... "
"So, where can we intuitively reflect the resistance in the air? When it rains, you need to hold an umbrella, and when the wind blows, the umbrella will sometimes be blown away. I wonder if you have ever discovered this truth."
After Li Zhen finished speaking, Liu Jinghong shouted: "Does the larger the area, the greater the resistance when facing the wind?"
"You can say that."
Li Zhen added: "There is resistance and power in the air; and aerodynamics simply means how to determine the best balance of these two completely opposite forces at certain times. In actual operation, it must be consistent with the air flow caused by environmental factors. pressure hook. Otherwise you will not be able to distinguish between aerodynamic force and air resistance... "
"Due to the effect of air resistance when an object moves forward at high speed, it generates aerodynamic forces in three directions: longitudinal, lateral and vertical around the center of gravity of the object. Among them, the longitudinal air force is the largest air resistance, accounting for approximately 10% of the total air resistance. More than 80% of the resistance…”
Lin Xiufeng was taking notes anxiously. He felt that he couldn't understand it at all.
The Book of Heaven is purely the Book of Heaven.
Although Li Zhen tried very hard to explain from the simple to the deep, he still couldn't understand. I understand the truth, but... I always feel that it is indescribable.
Qin Enze asked: "The reason why birds can fly into the sky is because they have wings. So, does it mean that the wings of birds flap like fans, forming a reaction force in the air, thus obtaining Lift?"
Li Zhen's eyes lit up: "Yes. Although there are many more complicated things in it, this is indeed the principle."
Qin Enze nodded and sat down, as if he was in a trance and didn't know what else to think about.
Liu Jinghong also suddenly asked: "So, if humans want to fly into the sky and create a device with wings, can we make those two wings gain power and flap the air to generate upward lift? , the downward reaction force lifts off?”
Li Zhen waved his hand: "It's complicated. Your idea is not wrong, but I said that the principle of birds flying into the sky is extremely complicated. It is not what you think. And if humans want to fly into the sky, they are not necessarily rigid. It is based on the principle of birds. We can also use other principles to do it. Don't interrupt my lecture, I will continue."
“…”
"The study of aerodynamics is divided into two aspects: theory and experiment. Theoretical and experimental research are closely integrated with each other and complement each other. The general principles based on theoretical research are: In terms of kinematics, follow the law of conservation of mass... Follow the law of conservation of energy... "
“…”
After finishing the lecture on physics, Li Zhen had lunch and came to the School of Mathematics.
A group of people in the School of Mathematics who were waiting for food looked at Li Zhen with some nervousness and fear.
Recently, they have discovered more and more that advanced mathematics can really teach people to death.
Throwing out a concept has already driven several people crazy during after-class research. Everyone was a little frightened. This human thinking is really... too scary.
Why are people’s minds so big? Why is it so big
Isn’t mathematics just addition, subtraction, multiplication and division? Isn't mathematics the calculation of how much a pound of pork is worth if Xiao Ming bought two kilograms of pork for twenty yuan
Mathematics... why after learning it, it is not a number at all. Why have they become all kinds of letters, all kinds of formulas, all kinds of thinking patterns, all kinds of concepts...
Going crazy.
"Hello Master Li."
Li Zhen nodded: "Okay, let's talk about algebraic functions today."
“…”
"Non-transcendental functions are called algebraic functions. Examples of algebraic functions include polynomials and square root functions. The indefinite integral operation of a function is a rich source of transcendental functions, such as the logarithmic function, which comes from the indefinite integral of the reciprocal function... "
You look at me, I look at you.
Can't understand.
I should have known about physics.
I should have known about chemistry.
Even Hou Qiang, a great figure in mathematics, was completely confused at this time.
A girl pushed Hou Qiang and whispered: "Have you ever heard of a math class that is all about words and not a single number?"
Hou Qiang smiled bitterly: "Aren't you learning?"
“…”
Li Zhen's lectures were eloquent.
But at this time, something like this happened in Kyushu Physics.
Qin Enze was stunned. He sat in the laboratory and murmured to himself: "Why do humans fly into the sky? Obviously, it is impossible to fly into the sky with wings. Master Li said that humans do not have such muscles, it is impossible It relies on the power of its hands to stir up the air and make itself airborne. And machinery, or steam, is simply not enough to make the device flap its wings."
"But I can definitely fly into the sky. It's absolutely no problem."
"If humans want to fly into the sky, they only need two forces. Upward lift and forward momentum."
Qin Enze murmured, lit his pipe and took a deep breath. Suddenly a light flashed in his eyes, and a thunder resounded in his mind.
"If the steam engine can replace forward power, then it only needs to obtain upward lift to achieve the effect of flight. It does not specifically require the wing structure of a bird. The problem of forward power does not need to be solved now. Now I have to personally prove the upward lift..."
After taking a look at the physics laboratory, where everyone was arguing, Qin Enze silently walked out of the physics laboratory with his pipe in hand.
The first to eat crabs, the first to take risks.
Li Zhen was the first person in Kyushu to propose air resistance, and Qin Enze will be the first person in Kyushu to prove air resistance.
Aerodynamics must combine theory and practice, and proof is indispensable. Crazy Qin Enze is about to prove the existence of air resistance.
When Li Zhen walked out of the School of Mathematics dizzily, the entire Kyushu Academy of Sciences suddenly went into shock, with screams and cries rising one after another.
"Qin Enze is going to jump off the building!"
"Master Li, it's not good, Enze is going to jump off the building!"
"Quick, call the doctor. Get the sheets and put them underneath."
"Qin Enze can't make any mistakes. He is the mainstay of the Institute of Physics."
"Oh, Enze, why can't you figure it out? Why did you jump off the building?"
"Enze, if you can't figure out the academic issues, you can think about it slowly. Why are you seeking short-term advice?"
“…”
The entire Kyushu Academy of Sciences was shocked, and everyone rushed out to the tallest teaching building. There are ten floors in total and more than thirty meters high.
Li Zhen's expression changed wildly, he dropped the book and ran away.
When he arrived at the top of the teaching building, he saw Qin Enze waiting for something with his eyes closed on the edge of the rooftop above. He was mumbling something.
"Enze!"
Li Zhen yelled: "Come down!"
(End of chapter)