It's a dream,

Xu Mang became the father of two children in his dream, the children are very smart, have good academic performance since childhood, and are very filial, and get the scholarship every year, but when he got the junior son Xu Yang in high school, he fell in love, and also found an airport with a height of less than one meter five and came back, Xu Mang was so angry that he vomited blood.

"Hey!"

"Professor Xie is calling you!"

"Wake up!"

Suddenly hearing someone shouting to himself, Xu Mang opened his confused eyes, and saw a girl staring at him in front of him, and instantly fell into doubt, did he have a relationship with her? But to be honest... She looks average, and she is not a little worse than Xiao Man.

"Huh?"

"Who are you?" Xu Mang looked at her curiously, his face full of doubts and puzzles about the situation in front of him, but soon he realized that something was wrong, and the atmosphere of the entire classroom seemed to fall into silence, and everyone around him looked at him.

This... What's going on?

Why do people suddenly care so much about me? Have you forgotten your glasses?

Xu Mang hurriedly touched his black-framed glasses, and the glasses were hanging on his face, which is very strange, although a pair of glasses can't change anything, but it does change his temperament, and his temperament has changed... And people have changed.

"This classmate!"

"Have you learned physics very well?" Professor Xie asked solemnly: "Then to solve the problem I just mentioned, two identical charged particles with mass m and charged e, start to be far apart, one particle is stationary, and the other is moving towards the stationary particle with a velocity v and an aiming distance p equal to 2ke^2/mv^2. ”

"So what is the neutralization scattering angle of the centroid system?" Professor Xie asked, "You answer." ”

Yes?

Particle system dynamics?

I didn't write about it.

Xu Mang recalled that when he wrote the dynamics of the particle system, he did not write any questions about the dynamics of the particle system, and it is estimated that this topic was written by himself on an improvised basis, but it is indeed a very good problem, which involves the translational reference frame of scattered particles and the formula of kinematic equations under the action of the inverse square force.

Of course

This is just one of the solutions, and there are actually many ways to solve this problem, each of which is different, but the answer is almost the same.

"Oh..."

"I... Did I go to the blackboard to write the process?" Xu Mang asked curiously.

"Yes!"

"Go to the blackboard and write. Professor Xie said seriously: "That's right... If you can't write this question, my basic physics course... You have to retake, and if you are satisfied with the process and the answers, and I don't need to come to the class in the future, I will give you a perfect score. ”

Hiss!

it!

Play so big?

Hearing Professor Xie's words, many people present gasped, don't be scared, but it is more of a kind of remembrance of Xu Mang, he did not hesitate to use his own failure to verify a legend of the School of Physics, that is, don't talk back to Professor Xie, it's easy to go around without eating.

Xu Mang got up and walked through the crowd, under the gaze of a heroic expedition, all the way to the blackboard, silently wrote the previous question of Professor Xie, and then stood in front of the blackboard, looking at the topic in front of him, he was a little stunned for a while.

It seems like...

There's not enough blackboard!

"Ahem!"

"Professor Xie?"

"What should I do if the blackboard is not enough?" Xu Mang asked cautiously, "These four big blackboards are not enough for me to write... What if this is broken in the middle?"

Professor Xie frowned, his eyes were full of doubts, and he said seriously: "Impossible! This is my topic, let alone four blackboards, two blackboards are enough, in short, you can write... If you can't write it, tell me, I won't be in class today, it's all up to you to solve the problem. ”

“...”

"Oh!" Xu Mang nodded, helplessly picked up the chalk at hand, and wrote the word 'solution' steadily with skin, feeling a little twisted, and hurriedly added a colon, comfortable...

I have to say,

I'm used to writing papers, and then I go back to solve such ordinary problems, so I'm not used to it.

originally

Everyone was not optimistic about Xu Mang, including Professor Xie, but when Xu Mang came up with an arithmetic process based on the translational reference frame of scattered particles, Professor Xie realized that things were not as simple as he imagined.

Followed by

Professor Xie saw a very perfect calculation process of kinematic equation formulas under the action of inverse square law, and couldn't help but show a trace of surprise, but this surprised expression lasted for a short time, and soon returned to normal, scattering particles translational reference frame, and the kinematic equation formula under the action of inverse square law, which could not explain anything.

The real difficulty is in the back, you need to draw a flat two-dimensional diagram, and calculate the subsequent process according to the two-dimensional diagram.

Boom,

Xu Mang continued to solve the problem, but the speed was a little slow.

Wait a minute!

When Professor Xie saw Xu Mang writing a set of relationships, m1 and m2 were the masses of scattered particles and scattered particles m1=m2=m, respectively, his expression gradually changed from cold to a little panicked, and sure enough... He saw a particle group relationship that Xu Mang had envisioned.

Let the velocities of particles 1 and 2 with respect to the translational reference frame of the center of mass be v1c and v2c, respectively, parallel and opposite, because m1=m2=m, v1c=v2c, vr=v1c-(-v2c)=v1c+v2c=2v1c.

This...

This student... It's not easy!

Have you already learned all the contents in advance?

meanwhile

The students in the audience were a little shocked, they never expected that the contestant who was originally considered to be the bronze rank would turn out to be the king rank, especially the two girls who sat in front of Xu Mang before.

"He..."

"That's amazing!"

"This guy shouldn't be pretending to be a pig and eating a tiger, right?" The girl who woke up Xu Mang said to her best friend: "Peking University... It's like a place like Crouching Tiger, Hidden Dragon. ”

"That's all I said... The more people who don't seem to care, the more likely they are to be peerless geniuses. The girlfriend smiled and said, "Do you still question my words? He must be a genius... Just from that decadent energy, not a genius... God won't say yes. ”

"Cut!"

"I refute!"

"Professor Xu of Fuda is not the kind of person you are talking about. The girl said disdainfully: "Professor Xu is a genius among geniuses, but at the same time he works very, very hard, I think... Genius and hard work are always linked. ”

At this point,

Xu Mang's problem-solving process is still continuing, but it is about to reach the end, but in just ten minutes, Xu Mang has conquered everyone present, including Professor Xie who was standing on the side, he never imagined that there would be such a student.

Perfect!

It's perfect!

It turned out to be exactly the same as his own answer, and there was not even a single symbol wrong.

Professor Xie saw that Xu Mang had solved his problem very smoothly, and couldn't help but say, "Okay!

Halfway through the conversation,

Xu Mang came to the two blackboards that could be moved up and down on the side, and continued to write about the problem-solving process, but his strange behavior made many people a little confused, obviously the problem had been solved, why was he still writing?

This...

What is this doing?

Professor Xie was about to open his mouth to speak, but the next second, when the words came to his mouth, he forcibly held back again.

Centroid translational frame of reference?

This is...

The second solution?

Professor Xie was stunned for a moment, there is indeed a second solution, and it is very convenient, but it is not suitable for freshmen, he... How could he?

Impossible!

At this point,

Professor Xie became more and more curious about this student, and he stimulated himself again and again to refresh his perception of the freshmen, is he really a freshman? Or is he a junior or a senior or a graduate student who came to make trouble?

Three minutes,

All the students present witnessed the birth of a miracle, Professor Xie's problem, there seemed to be two completely different solutions, and the person who did this, he turned out to be the bronze contestant who had slept in the classroom before.

"Holy..."

"Who is this guy? Why haven't I seen him?" asked one of the students with a puzzled face, "Have you seen him? There's no hint of youth at all, and... How I look at his lazy look, how my heart twists. ”

"That's right!"

"But people are better than us. The boy on the side sighed: "It's so stressful... It would be great if I had the same talent as Professor Xu. ”

"Huh!"

"You're thinking about fart!" The boy sneered disdainfully, and then continued to look at the blackboard, the second problem-solving process, looking at the problem found, the boy suddenly felt that the back of the student answering the question seemed to have been seen somewhere.

This back...

It's so familiar!

“...”

"Am I hallucinating?" the boy said cautiously, "I... I think his back is a bit like Professor Xu!"

"You're!"

"Before, you thought that your girlfriend was behind a certain female star, and it was because of this relationship that you were with someone else, I watched... Like a fart!" The boy next to him said angrily: "Professor Xu is busy, how can he be so boring?

"Yes!"

After a few more minutes,

Xu Mang had already completed the second problem-solving process, but the space left for him was only half of the blackboard.

What to do?

How should the third type of office be presented?

Time

Xu Mang stood stupidly in place, not knowing what to do.

At this time, Xu Mang was on the rise, and finally had a feeling of youth, but this feeling was too short, not even half an hour.

"This classmate!"

"You are very good!" Professor Xie showed a satisfied smile and said to Xu Mang: "You have greatly exceeded my expectations, these two methods can be mastered at the same time, it is not simple... And it doesn't drag mud and water, the whole process is not a trace of superfluity, not bad, very good!"

Xu Mang shrunk his neck and said cautiously: "There is a third way to solve the problem... But I can't write it anymore. ”

......