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 mouths excitedly and nervously, staring at Li Zhen burningly.

"Air resistance. Who will say what air resistance is? ”

Xiao Shengnai raised his hand and stood up: "Master Li, when you talked about fluid mechanics, you once talked about resistance. So by reverse, air resistance is similar to that kind of resistance in fluid mechanics? ”

Li Zhen sat him down and said, "Tell me in detail." Air resistance refers to the obstructive force of air on a moving object, which is generated by the elastic force of air on a moving object. When the object is moving forward, the drag caused by the compression of the air in front of it, the friction between the surfaces and the air on both sides, and the space behind the tail becomes a partial vacuum. When running against the wind, the wind should also be added to the ......"

So, where can the resistance in the air be intuitively reflected? When it rains, you have to use an umbrella, and when the wind blows, sometimes the umbrella will be blown away. I don't know if you've ever discovered this. ”

After Li Zhen finished speaking, Liu Jinghong shouted: "Is it true that the larger the area, the greater the resistance when the wind is headwinded?" ”

"So to speak."

Li Zhen said again: "There is resistance in the air, power; Aerodynamics is simply how to determine the optimal balance of these two completely opposite forces at some point. In practice, it should be linked to the pressure of the air flow caused by environmental factors. Otherwise you won't be able to tell the difference between aerodynamics and air resistance......"

"Due to the action of air resistance in the forward high-speed motion of the object, the aerodynamic force in three directions such as longitudinal, lateral and vertical is generated around the center of gravity of the object at the same time, of which the longitudinal air force is the largest air resistance, accounting for more than 80% of the overall air resistance......"

Lin Xiufeng was anxiously taking notes, and he felt that he couldn't understand it at all.

The Book of Heaven is purely the Book of Heaven.

Although Li Zhen has tried very hard to speak from shallow to deep, he still can't understand it. I understand the reason, but ...... I always feel 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 a bird flapp like a fan, creating a reaction force in the air and thus gaining lift? ”

Li Zhen's eyes lit up: "Yes." There are a lot more complex things out there, but it's true. ”

Qin Enze nodded and sat down, his whole person was in a trance, and he didn't know what to think again.

Liu Jinghong also suddenly asked: "So, if human beings want to fly into the sky." By making a device with wings, can we make those two wings slap the air by gaining momentum, creating an upward lift and a downward reaction into the air? ”

Li Zhen waved his hand: "It's complicated." You're not wrong in your thinking, but as I said, the principle of birds flying into the sky is very complex. Not what you think. And if humans want to fly into the sky, they don't have to be bound by the principle of birds. We can do it with other reasons. Don't interrupt my lecture, I continued. ”

“……”

"The study of aerodynamics is divided into two aspects: theoretical and experimental. Theoretical and experimental research are closely integrated and complement each other. The general principles on which the theoretical study is based are: in terms of kinematics, the law of conservation of mass is followed...... Following the Law of Conservation of Energy......"

“……”

After talking about physics, Li Zhen had a lunch and came to the School of Mathematics.

A group of people in the Mathematics Academy who were waiting to be fed looked at Li Zhen, and they were all a little nervous and afraid.

Lately, they have been discovering more and more that this advanced mathematics can really learn from the dead.

A concept is thrown out, and several of them have been driven crazy in the after-class research. Everyone was a little frightened, this human mind is really ...... It's horrible.

Why is the human brain so big? Why is it that big?

Isn't math addition, subtraction, multiplication, and division? Isn't mathematics calculating how much Xiao Ming bought two catties of pork and spent twenty yuan to find out how much one catty of pork is equal to?

Mathematics...... Why is it not a number at all? Why have they all become all kinds of letters, all kinds of formulas, all kinds of thinking patterns, all kinds of concepts......

It's going crazy.

"Master Li is good."

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, for example, the logarithmic function comes from the indefinite integral of the reciprocal function......"

You look at me, I look at you.

Do not understand.

I already knew how to study physics.

I knew I was studying chemistry for a long time.

Even the math math bull Hou Qiang was completely stunned at this time.

A girl pushed Hou Qiang and said in a low voice, "Have you ever heard of a math class full of words and no numbers?" ”

Hou Qiang smiled bitterly: "Isn't this learning?" ”

“……”

Li Zhen's lecture was overwhelming.

At this time, such an incident happened in Kyushu physics.

Qin Enze was stunned, sitting in the laboratory and muttering, "Why do human beings fly to the sky? Obviously, it is simply impossible to fly with wings. Master Li said that human beings do not have such muscles, and it is impossible to use the power of their hands to stir up the air and make themselves take off. And machinery, or steam, is simply not enough for the device to stir up its wings. ”

"But I'll be able to take to the skies. Absolutely. ”

"If humans want to take to the skies, they only need two forces. Upward lift, forward momentum. ”

Qin Enze muttered, lit his pipe and took a sharp breath, his eyes suddenly flashed, and a thunderbolt resounded in his mind.

"If the steam engine can replace the forward power, then only the upward lift is needed to achieve the effect of flight, and it does not specifically require the wing structure of birds. The problem of forward momentum does not need to be solved now, I now have to prove the upward lift for myself......"

Glancing at the physics laboratory, everyone was arguing, and Qin Enze silently walked out of the physics laboratory with a smoking gun.

The first to eat crabs, the first to take risks.

Li Zhen was the first person in the entire Kyushu to propose air resistance, and Qin Enze would be the first person in Kyushu to prove air resistance.

Aerodynamics must be combined with theory and practice, and it is indispensable to prove that the crazy Qin Enze is about to prove the existence of air resistance.

When Li Zhen walked out of the School of Mathematics dizzily, suddenly the entire Kyushu Academy of Sciences was in a sensation, screaming and crying one after another.

"Qin Enze is about to jump off the building!"

"Master Li, it's not good, Enze is going to jump off the building!"

"Quick, call the doctor. Grab the sheet and pick it up below. ”

"Qin Enze can't make a mistake, he is the mainstay of the Academy of Physics."

"Oh, Enze, why can't you figure it out, why do you want to jump off the building."

"Enze, if you can't figure out academic issues, you can think about it slowly. Why look short. ”

“……”

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 face changed wildly, and he threw down the book and ran away.

When he arrived at the bottom of the highest teaching building, he saw the edge of the rooftop above, Qin Enze was waiting for something with his eyes closed. He was muttering something.

"Grace!"

Li Zhen yelled: "Come down!" ”