Jiang Mubai tempered his physique, his eyes were full of stars, and Dai Qiuzhen could see at a glance that he was a martial artist, so he was even more curious.

"Gases and liquids are fluids, and the movement of objects in fluids will be affected by fluids, for example, when a railway train is moving at high speed, the air in front of the locomotive is compressed, the surfaces on both sides rub against the air, and the vacuum behind the rear of the train will have an impact on the train and produce resistance. Oh, and drag is the force that hinders the motion of an object. ”

Knowing that his science knowledge reserve was insufficient, Jiang Mubai explained out loud without waiting for Dai Qiuzhen to ask questions in order to grasp the direction of the dialogue.

"The magnitude of air resistance is related to factors such as air density, object movement speed, contact area, etc., your sword is not deformed, but the speed back and forth is different, as far as I know, air resistance is proportional to the square of the object's movement speed, the faster the long sword flies, the greater the resistance, and the more energy needs to be consumed."

Under the gaze of the strange eyes of the senior brother and sister, Jiang Mubai was out of breath, and continued: "Of course, the actual situation is very complicated, not only the air resistance must be considered, but also the kinetic energy you inject into the long sword, the kinetic energy is one-half of the product of the square of the mass of the object and the velocity, the mass of the long sword remains the same, and the speed increases, the kinetic energy increases, which also requires you to consume energy." ”

"Maybe the energy conversion efficiency has something to do with the distance between you and the sword, which further leads to more consumption. Also, consider the time the longsword stays in the air, because gravity always acts on the longsword, and the longer the longsword stays in the air, the more energy it takes to overcome gravity. From this point of view, the faster the speed, the shorter the time spent in the air, and the less energy is expended to levitate the sword. ”

Dai Qiuzhen nodded again and again, and a smile appeared on his serious face.

"The little brother looks like a talent, why don't you talk about people?" Susie rubbed her eyebrows and pretended to have a headache.

Qiu Yi threw a look at Shi Guangwen to express his doubts, and Shi Guangwen shrugged his shoulders and said, "I don't understand what Senior Brother Jiang is saying, and I don't know where he learned it." ”

"I learned it from a book!" Jiang Huiyin raised his head, extremely proud, "My brother was admitted to Tianjing University, and he stayed in Dingwu to take care of me." ”

"Oh yes, I know that." Shi Guangwen nodded to corroborate.

"I see." Qiu Yi was stunned, and when he turned his head again, he was already impressed by the little junior brother.

"This classmate is roughly right."

On the podium, Dai Qiuzhen held the hilt of the sword and slowly pulled out the long sword, and while showing it to the students, he said: "We know that the gravity of an object is proportional to its mass, well, it doesn't matter if you don't understand it, let me put it another way, the heavier the thing, the more effort it takes to lift it." I would like to ask everyone, why do you have to refine such a sword into a magic weapon? Martial arts practice sword fighting, so we need a sword hilt, we practice the sword, what is the use of this sword hilt? With this hilt, not only does the mass increase, but the air resistance when flying is greater, isn't it? ”

"Teacher Dai, the hilt of the sword is useful." Objections rang out in the classroom, "I see that several teachers in the Edgeworth Department are flying sideways with the hilt of their swords in their hands when they are flying at high altitudes or at high speeds. ”

"Imperial weapon flying may not only be with a sword, stepping into the Xuan Realm will have an extraordinary qualitative change, and it is not difficult to refine an additional flying magic weapon. Furthermore, you are all cultivators of the first and second realms, and you have neither the ability to fly with your sword, nor the martial arts to dance your sword to kill the enemy, so why do you use such a sword? ”

Dai Qiuzhen smiled at the bar spirit, spoke softly, and then summoned a sword blade without a hilt.

The blade is symmetrical anteriorly anterior, with open edges on both sides, grooved on both sides, and the tip of the head and tail of the sword protrudes into a pointed wedge-shaped structure.

"Look at this sword, it's lighter, it's more agile, and there's less air resistance when flying. If one day you were to go into battle, which sword would you choose? ”

"But, all the Fa cultivators I've seen use swords with hilts?" The bar spirit lifts the bar again.

Dai Qiuzhen waved his hand: "First of all, there are many kinds of magic weapons and magic weapons, and most of the swords are just decorations, and secondly, what I want to tell you is not that swords with hilts cannot be used, but that we can learn to master the principle of changing things, so as to get twice the result with half the effort." Take magic weapons as an example, if you master the theoretical knowledge required for casting magic weapons, you can design and cast your own natal magic weapon according to your own preferences and needs. ”

"With this kung fu, it's better to stay in the meditation room and practice, if you go up to the realm, you won't be able to break through the trick with your strength, besides, there are a lot of people who study these, why should we learn, and I haven't heard of any real person who put down the scriptures to learn any useless science."

The bar spirit was so persistent that Jiang Mubai suspected that this was a compliment invited by Teacher Dai.

Dai Qiuzhen's good temper seemed to have worn out, he glared at Gong Jing, and said coldly: "Yang God can be called a real person above, do you know how many registered Qi cultivators are in the Second Domain?" What about Tongxuan? What about the Yang God? Is it still empty? How many of you can be the 1 in 10,000, 1 in a million and 1 in 10,000? Science is useless? Joke! ”

Gong Jing sneered, threw away the elective textbook in his hand, rolled his eyes and strode away, the classmates who came with him tried to dissuade him, but he didn't care.

Dai Qiuzhen stepped down from the podium, picked up the textbook, dusted off the dust, and said expressionlessly: "I believe everyone has heard of the Izumo Sect's Heavenly Sword 'Cutting Clouds', today I will tell you what the Heavenly Sword 'Cutting Clouds' that kills the Heavenly Demons is." ”

"The Sky Sword 'Cutting Clouds' is a tungsten gold flying sword carried by a low-earth orbit satellite. Have you ever seen a high-altitude projectile? To put it simply, a cut cloud is a sword-shaped object thrown to the ground from thousands of kilometers in the air. ”

"This student just said that the kinetic energy of an object is equal to one-half of the product of the square of the mass of the object and its velocity, so if we want to strike at a target through a physical medium, why do we have to fight against gravity? Why not let gravity power our weapons? ”

"Students, we are Fa cultivators, we have supernatural abilities that the science of the old era cannot explain, but this does not mean that we have to overthrow all the knowledge systems of the past, even the Izumo Sword Sect will use the gravitational potential energy to fight against the Heavenly Demons, why do we abandon the natural sciences as if they were gone?"

"As early as more than a hundred years ago, someone in the Third Domain had already put forward the idea of space-based weapons, but it never succeeded, why? Because the efficiency is not high, because the accuracy of the strike is insufficient, there are various reasons...... Then why is the principle of Heavenly Sword's 'Cloud Cutting' similar, but it is so successful? Because of the Izumo Sword Sect! It was the Izumo Sword Sect that turned the impossible into a possibility and a joke into a myth! ”

"Therefore, science is not useless, on the contrary, science is a more useful tool in our hands, and if you master it, you will also have the potential to turn decay into magic."

It turns out that the famous Heavenly Sword Cutting Cloud is the space-based kinetic energy weapon system that was jokingly called "God's retardation" back then.

It turned out that the Izumo Sword Sect was able to make up for the many shortcomings of the Staff of God, making it a powerful magic weapon to bombard the Heavenly Demons.

Jiang Mubai's heart was turbulent, and out of the corner of his eye, he caught a glimpse of a middle-aged man in a robe showing his figure in mid-air, he nodded slightly at Dai Qiuzhen in approval, and then a blazing light gushed out from the soles of his feet, enveloping his whole body in an instant.

Respectfully?

As soon as the thought came to him, the light cluster had risen to a height of 100 meters and flew into the air attic suspended above the campus.