The truth is all told to others, Chen Ge doesn't know if he will be the same as Zhang Tianjiao when he encounters this kind of thing, but he still has to say what he should say as a brother.

Chen Ge didn't plan to go to the afternoon class, but at three o'clock he received a message from Ma Min to himself: Chen Ge, you dare to skip my class, you are limited to ten minutes, otherwise you will bear the consequences.

Chen Ge remembered Ma Min's vicious gritted teeth, opened his teeth and danced his claws, and couldn't help but shudder, said hello to Li Yue and the others, and hurriedly ran to the classroom.

When Ma Min arrived in the classroom, he had already started to lecture, Chen Ge sneaked in through the back door, looked left and right and found that Wang Qixuan was also there, and quietly walked next to Wang Qixuan.

Wang Qixuan couldn't help frowning when she found someone sitting next to her, looked up and saw that it was Chen Ge who stretched out, and asked in a low voice, "Why didn't I see you in the morning." ”

Chen Ge said: "Our class schedules seem to be different. ”

Wang Qixuan said: "No, I will refer to your class schedule in the morning. ”

Chen Ge immediately grasped the point, "You said that you deliberately went to audit my class schedule in the morning?" ”

Wang Qixuan blushed, "Don't get me wrong, I wanted to ask you something, I forgot it at the subway entrance yesterday afternoon." ”

"What is so important, and I deliberately refer to my class schedule to attend classes." Chen Ge focused on two words.

Wang Qixuan said: "The question is not important, but I don't ask clearly, I feel uncomfortable, I have obsessive-compulsive disorder." To be serious, did you write the poem you gave me after class a few days ago? ”

Chen Ge looked disappointed, "Oh, it turns out that this is the problem. ”

Wang Qixuan said: "Then what do you think, is it or not?" ”

Chen Ge asked rhetorically: "Then have you heard this poem before?" ”

Wang Qixuan shook her head.

Chen Ge asked again: "Then can you search for it in Baidu?" ”

Wang Qixuan continued to shake her head.

Chen Ge said: "That's what I wrote. ”

At this time, a person behind him poked Chen Ge heavily, and Chen Ge looked back to see that it was Liu Feng, the student who made a stumbling block for himself at the orientation party.

"What do you mean?" After Chen Ge questioned Liu Feng, he found that the situation was not quite right, because everyone seemed to be looking at this side, Chen Ge looked back at the podium again, and Ma Min was looking at him coldly.

"Classmate Chen Ge, I just wanted you to answer the question, but you didn't respond after calling you six times in total, only to see that you were endlessly disturbing classmate Wang Qixuan. Liu Feng kindly reminds you that you seem to be very dissatisfied, since you like to disturb the surrounding students so much, you must feel that the teacher is too in-depth today to learn again. Ma Min wrote a physics problem on the blackboard, "Now please solve this problem on the blackboard." ”

Chen Ge stiffened his head at Ma Min's gaze and said, "Okay..."

On the blackboard is a proof question: What is the pressure at the center of a star with uniform density due to gravitational pull?

Ma Min almost laughed in his heart, this physics proof question is not difficult, and there are misunderstandings that are easy to misunderstand, there are not many people here who can make this question, not to mention that Chen Ge didn't listen to what he just said, hum, see if you dare to skip my class again in the future, and openly hook up with girls in my class.

Chen Ge didn't speak for a long time, staring at the question on the blackboard with a blank expression.

Liu Feng is definitely the happiest person present, from the beginning of the orientation party, Liu Feng dreamed of seeing Chen Ge make a fool of himself, and he felt that the question on the blackboard was not small, and he might have to take it back to the dormitory to study it carefully, not to mention that Chen Ge was a scumbag with an IQ of only 5.

"Teacher, I think this question is problematic in the first place." Chen Ge pondered for a moment and spoke.

Liu Feng almost couldn't help laughing, no one in the school knew that Ma Min was notoriously rigorous and careful, how could he make a mistake, this stupid bi really dared to say it.

Chen Ge said: "I think the problem itself is not rigorous, according to the formula of gravitation, two objects cannot be infinitely close. According to the formula of gravitational force, the pressure at the center of each sphere (that is, the abstract point) is infinite, of course it is not true, in fact, when r is less than a certain degree dù (about the atomic magnitude 10^-10), gravitational force is no longer dominant, and the microscopic world is actually electromagnetic force, the world of strong forces. In other words, gravitational force is mainly a formula for the macrocosm, and since you are asking about the pressure of gravitational force, the conclusion must be an approximate formula. That is, the smaller the scale, the greater the error of the formula. Of course, it's a different story if it's a liquid planet, because the liquid transfers the pressure down. ”

Chen Ge walked up to the podium and listed the formula while explaining: "Now calculate the pressure at the center of the sphere of the liquid planet. Suppose the density of the liquid planet is p and the radius is R.

First, calculate the strength of the gravitational field E at any radius r in the interior of the planet:

E=GM(r)/r^2=G*p*4π/3*r^3/r^2=4πGp/3*r=kr, here k=4πGp

Now make a slender cylinder liquid column from the surface of the star to the center of the sphere, the cross-sectional area of the cylinder is s, s is very small, and the pressure in the center of the planet is the gravitational force of this liquid column/s.

The small body element dV=sdr at r is subject to gravity

df=E(r)pdV=kr*p*sdr=kpsrdr

I integrate this force from the surface to the center of the sphere and get it

F=kpsR^2/2

pressure

P=F/s=kpR^2/2=2πGp^2R^2/3。 ”

Chen Ge dropped the chalk, "Teacher, please see if I understand it correctly." ”

No one in the class spoke, staring at the problem-solving process on the blackboard and Chen Ge who solved the problem with wide eyes open, and a few people who knew Chen Ge opened their mouths wide for a long time and did not react, and there was only one thought in their hearts:, what happened, this world is too crazy!

Ma Min didn't expect Chen Ge to really solve this problem flawlessly, his face was a little unbearable, and he coughed twice and finally regained his majesty and confidence as a mentor, "Do you think you can solve this problem very well." ”

Chen Ge said, "No. ”

Ma Min pointed to the door, "If not, stand at the door." ”

Chen Ge was honest and stood at the door.

"Squat down with your head in your hands, and remember not to make loud noises in class in the future."

Chen Ge looked at the ground with his head in his hands, and 10,000 grass and mud horses galloped in his heart, he didn't expect that a college student who was a two-life person would be punished by squatting in the corner.

In fact, Chen Ge was confused when he saw the physics problem on the blackboard, and after reading it several times, he felt more and more familiar, as if he had seen it somewhere, this situation was exactly the same as when he was writing a novel, but he didn't expect to solve this physics problem by relying on his memory and his half-baked knowledge in the end.