Jiang Yang: I Couldn't Quite Understand It

The Physics Olympiad, officially known as the National High School Physics Competition.

It was divided into preliminaries, semifinals, and finals.

The paper before Li Dong was a Physics Olympiad preliminary exam from previous years.

Li Dong took a deep breath and habitually scanned the distribution of points across the paper first.

Based on his past experience with ordinary Gaokao papers, physics was usually worth either 100 or 110 points.

But now...

[Total score: 400 points]

[Time limit: 2 hours]

"400 points?"

Li Dong clicked his tongue inwardly.

That was nearly as many points as an entire science comprehensive paper.

There were twenty-six questions in total.

The first fifteen were multiple-choice questions, including both single- and multiple-answer questions, each worth more than six points.

The rest consisted of five fill-in-the-blank questions and six major calculation problems.

"So this is the intensity of the so-called Orsay."

Li Dong was somewhat surprised, but even more than that, he felt eager to give it a try.

Over the past few days, he had been like someone holding a hammer, seeing nails everywhere and wanting to give each one a whack. This was perfect.

He looked at the first multiple-choice question.

Normally, the first question was a freebie meant to help candidates steady their nerves.

But when Li Dong saw the question clearly, his brows still rose slightly.

[1. As shown in the diagram, a semicylindrical body with radius R is fixed on a horizontal surface. A small ball of mass m is placed on top of it. The ball starts from rest at the highest point of the cylinder and slides downward. Ignore all friction. When the ball leaves the surface of the cylinder, what is the vertical height h through which it has fallen?]

At first glance, it appeared to be an ordinary high school circular motion problem.

An ordinary senior high school student might have directly applied the centripetal force formula, mg - N = mv²/R.

But there was a trap here.

The question did not provide the exact angle at which the ball left the surface.

So the candidate had to set up a polar coordinate system independently.

Or solve for the critical condition by combining conservation of energy with Newton's second law.

"Interesting. They were coming out swinging right from the start."

If this question had appeared on a Gaokao physics paper, it would definitely have been the final and most difficult multiple-choice question.

But on an Orsay paper, it was merely the first question.

Still...

Li Dong grinned happily, like Ximen Qing running into Pan Jinlian.

"For me right now, this kind of rigid-body motion model couldn't be easier."

He did not even need to draw a force diagram on scratch paper.

The buff from [Physics Perception] gave him a clear image in his mind.

The ball began sliding downward. Gravitational potential energy transformed into kinetic energy, while the normal force rapidly diminished as the angle changed...

"Conservation of energy: mgh = 1/2mv²."

"Centripetal force equation: mg(R - h)/R = mv²/R."

Combining the two equations.

2gh = g(R - h)

3h = R

h = 1/3R

In barely ten seconds, Li Dong checked option C.

The office was terrifyingly quiet. Only the faint scratch-scratch of pen tips gliding across scratch paper could be heard.

Although the surrounding teachers were busy with their own work, their gazes occasionally drifted this way.

Jiang Yang stood behind Li Dong. Watching the speed at which he answered questions, the anticipation on his face gradually turned into confusion.

He was a physics teacher, but honestly, he was just an ordinary teacher who had graduated from a second-tier normal university.

Teaching standard high school physics was no problem.

But these were Orsay questions!

If he had done that first question himself, he would at least have needed to draw a diagram, set up a system of equations, and spend two or three minutes working it out.

But Li Dong? He checked the answer the moment he finished reading the question?

This kid... he couldn't have guessed, could he?

Jiang Yang kept wondering. He had heard of this kind of problem-solving method before, but he had never seen it.

Old Yang, standing on the other side, found his eyes growing brighter and brighter.

He was a top student from Beijing Normal University, and his foundation from those years remained solid.

Though he did not teach physics, mathematics and physics were closely connected, and he could understand the logic involved.

When he saw Li Dong working on a question about "the motion of a charged particle in a non-uniform magnetic field," Li Dong's pen traced a spiral in the air before he directly wrote down a differential equation concerning the radius of curvature.

r = mv / qB(x)

That equation was university-level physics!

This kid... Old Yang's heart churned like a stormy sea.

If the earlier math problems could still be dismissed as coincidence, then instantly crushing several consecutive questions like this was unquestionably proof of real ability.

The way Old Yang looked at Li Dong changed.

By comparison, Jiang Yang seemed increasingly restless.

He could not understand Li Dong's leaps in reasoning, nor did he know whether Li Dong's answers were correct.

The feeling made him panic a little.

No, I need to find someone who understands this and have them take a look.

With that thought, Jiang Yang turned and slipped out of the office.

Inside the principal's office.

Smoke hung thick in the air.

Zheng Hua, the head of the physics department, sat on the sofa with a bitter expression.

"Principal Wang, it's not that I don't want to cooperate."

Zheng Hua sighed.

"You know the situation at No. 7 High School. All the promising students get picked off by No. 6 High School and No. 1 High School."

"The remaining students still have to prepare for the Gaokao. You're asking me to find people for the competition now? Where am I supposed to find them? It's not like we can force them."

Principal Wang, seated behind the desk, also wore a helpless expression.

"Old Zheng, I understand your difficulties, but this quota came directly from the municipal education bureau. They said we need all-round development and can't focus only on the Gaokao."

"Don't put too much pressure on yourself. We're not asking for prizes. As long as someone goes, fills out the paper, and doesn't hand in a blank sheet that looks too embarrassing, that'll be enough."

Just as the two men were airing their grievances.

Bang!

The office door was shoved open.

Principal Wang and Zheng Hua were both startled, their brows furrowing at the same time.

"Jiang? Don't you know to knock before entering?"

Principal Wang spoke with some displeasure.

Only then did Jiang Yang realize that he had been too rushed and quickly apologized.

"Ah, sorry, Principal Wang. I... I have something urgent to discuss with Department Head Zheng."

Zheng Hua's heart skipped a beat as he looked at the panting Jiang Yang.

"What happened? Did students get into a fight?"

After all, he was not only the head of the physics department, but also No. 7 High School's dean of students.

Student fights were not uncommon at No. 7 High School, as long as they did not lead to serious consequences.

But seeing Jiang Yang in such a rush, Zheng Hua had to ask.

"No, no." Jiang Yang hurriedly waved his hands.

"Department Head Zheng, you... you need to come to the office and take a look. A student is doing that Orsay preliminary paper, and I... I couldn't quite understand it."

Zheng Hua's brows furrowed even more tightly upon hearing that.

"Jiang, are you too idle? I was just discussing this with Principal Wang. Why did you give an Orsay paper to a student?"

He sighed and spoke earnestly.

"I know you want to complete the assignment, but you can't just mess around like this."

"Which student is doing it? Chen Yue? Mi Xia? Or Jiang Yizhou?"

Those three were considered the best physics students in their grade, but in Zheng Hua's eyes, giving them Orsay questions would still be pointless.

"No."

"It's a student named Li Dong."

Jiang Yang quickly explained.

"Li Dong?"

Zheng Hua searched his memory but had no impression of the name at all.

"I've never heard of him."

Jiang Yang then explained how Li Dong had solved the chain problem using the Micro-element Method.

"What? The Micro-element Method? The Momentum Theorem?"

Zheng Hua's expression changed.

As the head of the physics department, his level was naturally far above Jiang Yang's.

He also knew about Jiang Yang setting the wrong question, so he understood perfectly well how valuable that chain problem was.

If a high school student could skillfully use calculus to solve a variable-mass problem, it could absolutely not be explained away with the words "just coincidence."

"Let's go! Let's take a look!"

Without another word, Zheng Hua stood and headed outside.

Principal Wang handled administrative work and had no concept of things like the Micro-element Method. He only wanted to complete the task from above as soon as possible, so he hurriedly reminded him.

"Old Zheng, make sure you keep that participation quota in mind!"