Chapter 243 (2/2)
”Whatever you can, you can count on it.” After he rubbed Li Zheng's head, he went out of the classroom.
Turning around and closing the door, I ran into Lu Yang.
”Mr. Xie, the lab is almost finished. Let's go to dinner at home?”
”Well, take them.” He leaned against the door of the classroom and waved his hand casually.
”Are you not going?”
”I'll wait.”
”Oh...” Lu Yang glanced at the door and window, and found Li Zheng in the back of the classroom with great effort. Then he said, ”is Li Zheng back?”
”Well.”
”Why don't you go to the lab?”
”I don't think so.” Solution of its dispute in its mouth smoke smile way, ”roll call me.”
”Ah Lu Yang shivered and looked into the classroom.
Full of pity and pity.
What are you doing, brother
It's not good to make good use of your time?
”The boy's aura doesn't agree with me, but it's interesting.” He sighed, lighting the glass. ”Scientific research all leads to the same goal. Although I should prefer to see the wind, it's also a way.”
“！” Lu Yang is a shiver again, ”Xie teacher Are you praising him? ”
”Don't you know I think he's stupid?” How can I teach high school students? To amuse him, he is determined to be unable to work out the problem, so as to drive him home
”Hoo That's right... ” Lu Yang relaxed, ”I said, you teach guijianfeng at most.”
”It depends on the mood.”
”Hee hee...”
”Didn't you think I deserved it before?”
”I'm going, I'm going...”
……
In the classroom, Li Zheng took advantage of the waste heat of the soaring realm, and soon came up with a solution.
How much charge can a drop of water carry?
It was easy for him to sketch out a physical picture in his mind.
First of all, there is tension on the surface of the droplet, which causes it to contract.
The charge on the surface of the droplet expands due to repulsion.
When repulsion is equal to tension, water droplets will not be able to maintain their shape and then break up.
At this time, the amount of charge that produces repulsion is the maximum charge.
After he figured out the principle, Li Zheng did it.
In the case of no effect of gravity in vacuum, let the water drop be spherical, the radius is r, the density is ρ, the surface tension coefficient is σ, the carrying charge is Q, and the vacuum dielectric constant is ε.
Then, according to the ”slice analysis method” just learned, take a small element on the water drop for stress analysis
A little bit
A little more
No, draw a geometry
Damn it, curvature up
……
There it is!
The tension is 2 σ r!
The formula must be right.
And then there's repulsion
Cut it up. It's tiny.
Whatever, in fluid mechanics, differential is the sky.
Then calculate the electric field strength
Well I feel that Gauss theorem is going to be applied here
So in the end
The repulsion force is 12. ε (Q4 π ε r?)!
Let the repulsion force and tension be equal, and solve the equation
There it is!
Q=8π√εr³σ！
To put it simply, when Li Zheng did it, he was already sweating. To solve the dispute, he pinched his watch and pushed the door back to the classroom.
He walked all the way to Li Zheng, squinting and pinching the answer sheet.Then there was a stare.
”I'll go to your mother's house and do it?”
”Well, isn't it very difficult...” Li Zhengli cut out the lotus like hair, ”can you start to tell me about your research?”
”No This... ” The solution of its dispute for a long time also did not find the flaw, fidgety scratched his head, ”I did not finish the topic, this is the first question.”
“？？！” Li Zheng got up in surprise and anger.
Damn it! Learn ruffian!
”Don't worry, don't worry. The second question is very simple.” ”Listen, second question - please use another way to solve the problem.”
“？？？”
”Open your mind, half an hour.”
So he closed the door again.
Li Zheng was very angry.
Naturally, he can leave.
But that way, isn't it exciting to learn ruffian?
No!
Solution!
Hard solution!
Therefore, Li Zheng for the first time with hatred, to the topic of the face.
……
Half an hour later, Xie Qifen came into the classroom again, kneaded his stomach and walked to Li Zheng's desk.
When I picked up the scroll, I was furious.
”Shit!! How can you come up with this
”Hum.” Li Zheng wiped his forehead full of oil and said with a strong sneer, ”the principle of minimum action is just the content of ordinary undergraduate mechanics.”
”Third question!” The solution of its dispute a pat of paper, full of ferocious way, ”please come up with a solution.”
”Ha Ha ha... ” Li Zheng gave a sad smile and looked out of the window at the setting sun. He slowly took out the hidden paper from his desk. ”I'm sorry, I've already thought of this layer.”
“？！” The solution of the dispute suddenly shocked the whole person's world outlook.
He took the answer sheet rigidly. After only one glance, his hand dropped down.
”This is the first question that forces me to study the principle of virtual work.” Li Zheng chuckled and picked up his stationery. ”I know you don't want to teach me. Just say I'll go.”
”You You... ” Jieqifen looked at the paper all over the ground, scratched his scalp and said, ”please ask me again Maybe I'll promise... ”
”No Li Zheng carried his schoolbag and was proud of himself.
How can I bow to learning ruffians when I learn from demons?
His face was askew and he avoided the eyes of Justice: ”you, you can just say two good words and try...”
Li Zheng frowned and said, ”smoking is harmful to your health.”
“…… Oh, for the sake of your concern for the teacher's health, I'll teach you two classes
“……”
”Go, walk, eat first.” ”You can understand my research at this level,” he said
”To be clear, you have to teach me.”
”Hey, drink and talk.”
”Drink?”
”Let's go, let's go...” When he pushed Li Zheng, he found a piece of paper on his buttocks.
He twists up the paper to see, startled: ”you also prepared the fourth solution???”
”I'm sorry to say that...” Li Zheng Hufan started to say, ”this is the solution I got from asking outside, and I can't understand it myself.”
”You can't understand it.” He took a picture of the paper and laughed, ”the perturbation method is the method of Nobel Prize winner in physics. It's cheap to help your brother check the paper.”
”Shut up!” Li Zheng is impatient.
”Ah?” The solution of its confusion Leng for a moment, a pat head, busy change of mouth way, ”I understand, is not a friend, then she must also look up the paper, intelligent!”
”Well.”
……
Several kilometers away, Lin Yujing yawned, threw away the manuscript paper and went to the table.
This training seems to be very interesting?
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