Red Flowers, White Flowers

Soon, the bell rang again. This period was physics.

Liu Limin had not returned yet, so Li Dong continued sitting in the seat at the very back of the classroom.

After being utterly crushed in the previous biology class, he was now looking forward to this one.

He really wanted to see just how interesting a physics class at Jiangcheng's top high school could be.

After all, he could already foresee a bottleneck in his physics studies.

The problems he knew how to solve could not stop him at all. As for those he could not solve, he needed to fill in the missing links in his prior knowledge. But that was a systematic undertaking. Without someone to guide him, he might still manage, but he would take many detours.

"I'm really looking forward to this..."

At that moment, an elderly teacher with graying hair and glasses stepped onto the podium.

Chen Ke, the pillar of Jiangcheng No. 6 High School's physics department, was also the province's renowned former head coach of the Physics Olympiad provincial team.

Twenty-two national finals gold medals, one International Physics Olympiad gold medal, and countless domestic competition awards—those were the achievements of his coaching career.

"Students, today we're going to have some fun."

Old Chen placed his thermos on the podium and revealed a kind, amiable smile.

Yet at the sight of that smile, the Elite Class students below the podium all shuddered.

Last month, Qin Yan—the top student in the entire school, who had already won a national finals gold medal and secured a spot on the National Training Team—had fallen beneath that very "amiable smile." He had been stuck on a single problem for an entire class, and his face had turned green by the time the bell rang.

This old bastard was definitely about to stir up trouble again!

Old Chen ignored the students' resentful stares. Picking up a piece of chalk, he turned toward the blackboard and spoke as he wrote.

"We'll be breaking down a comprehensive rigid-body dynamics problem. It's adapted from a real IPhO problem from last year, and it was also this year's entrance assessment problem for the National Training Team."

The moment those words came out, the students in the classroom wore expressions that said, "Just as expected."

They naturally had done plenty of real Orsay problems before, but the deadly part was the word "adapted."

This old man loved heavily modifying problems. Often, changing the conditions did not actually increase the difficulty by much, but it made the angle of approach extraordinarily tricky.

Li Dong, sitting in the back row, excitedly adjusted his posture, ready to welcome a satisfying mental storm.

[As shown in the figure, a uniform solid sphere of mass M and radius R initially spins rapidly about a horizontal axis of symmetry with angular velocity ω₀, while its center of mass translates to the right along a rough horizontal surface with initial velocity v₀. The coefficient of sliding friction between the sphere and the horizontal surface is μ.

Find the time t required for the sphere to transition from its initial state to pure rolling, as well as the velocity v of its center of mass when pure rolling begins.

If the horizontal surface is not perfectly rigid, the rolling sphere forms a circular contact patch of radius a at the contact surface. Given a rolling friction coefficient δ, find the total distance L traveled by the center of mass before the sphere eventually stops rolling.

If the sphere's initial axis of rotation is inclined at an angle θ to the vertical direction, consider the precession caused by gravitational torque. Qualitatively analyze the changes in the sphere's rolling trajectory, and derive the expression for the precession angular velocity Ω.]

"Come on, put pen to paper and work it out. It's not hard."

Old Chen tossed aside the chalk and said with a chuckle.

Li Dong carefully read through the problem below and nodded in deep agreement.

It really was not difficult. This teacher was truly honest.

Just now, Li Dong had already run through the entire derivation in his head.

He uncapped his pen and began writing on his scratch paper:

"First part: the moment of inertia about the center of mass is J = 2/5 MR², the sliding friction force is f = μMg, and the acceleration of the center of mass is a = -f/M = -μg... For angular momentum about the contact point, since friction exerts zero torque about that point, the initial angular momentum is Jω₀ + Mv₀R = Jω + MvR. Combined with the pure rolling condition v = ωR, we can solve for v and t..."

Simply put, the first part was just a pure rolling problem, at most comparable to a mid-level Huaxuan Cup semifinal problem.

The second part was a rolling-friction problem involving a circular contact patch. It merely introduced an infinitesimal integral for the resisting torque.

Calculate the integral, obtain the resisting torque, then apply the work-energy theorem. It was just a tiny bit harder than the first problem, but no more than that.

As for the third part...

Others might think the precession effect was the hardest part, but Li Dong thought it was the easiest.

A precession problem? What a joke! Just a few days ago, while wearing the disguise of a "stupid nephew," he had discussed Mercury's perihelion precession and celestial orbital perturbations with Le Verrier and Newton in the group chat!

Compared with problems of that level, rigid-body precession within the framework of Classical Mechanics was child's play.

This problem did not even involve nutation. It was purely testing M = dL/dt.

Li Dong spent roughly three to four minutes writing down the final expressions for all three parts on his scratch paper. He even drew a force diagram of the precession trajectory beside them.

Done.

Li Dong put down his pen and looked up at the surrounding students.

The top students of No. 6 High School's Elite Class around him all had their brows tightly furrowed, tugging at their hair.

Seeing them like this, Li Dong pondered to himself.

"Looks like I'm probably a little better than them at physics. They'll likely need to work on it for a while longer."

Li Dong completely overlooked one possibility: these top students might not be able to solve it at all.

Since he had nothing better to do, and believing there was no point wasting time,

the student who had only entered No. 6 High School that day started playing on his phone during his first physics class in his new classroom...

Old Chen, standing at the podium, had originally been smiling with his hands clasped behind his back as he watched these geniuses, who were usually so full of themselves, scratch their heads in distress.

Then he suddenly spotted Li Dong in the corner of the classroom.

Old Chen narrowed his eyes slightly.

This student looked unfamiliar, but the Elite Class used a fluid system, so it was normal for him not to recognize everyone.

What puzzled Old Chen was not the unfamiliar face, but the fact that this student... was actually playing on his phone with his head lowered?

After teaching at No. 6 High School for so many years, Old Chen had not seen such an arrogant little brat in a long time.

But he did not get angry.

Because anyone who could sit in the Elite Class could not possibly be a hopeless poor student who had given up on himself.

Since he was not unwilling to study, there was only one possibility—he had finished it.

Old Chen subconsciously checked the time.

Just over five minutes.

And judging from the boy's appearance, he had probably been playing for a little while already.

He had given this problem to Qin Yan before. Qin Yan had taken seven minutes to derive the correct expression for the third part.

This kid had finished it in under five minutes?

He had no idea whether the answers were right.

He slowly stepped down from the podium and wandered toward the back of the classroom.

At that moment, Li Dong's entire focus was immersed in the Azure Dragon Study Group.

Recently, Newton had been tearing through the Second Industrial Revolution like a madman.

[Isaac Newton]: Everyone, the improvements to my internal combustion engine have been a great success. The stability of the four-stroke cycle has exceeded expectations, and the high-pressure steam engine has also matured. We have already applied them to deep mine drainage and preliminary railway transport tracks!

[Isaac Newton]: Our industrialization process is exploding at a geometric rate!

Even through the screen, Li Dong could feel Newton's arrogant confidence in grasping the pulse of the era.

But then...

[Isaac Newton]: However, I have encountered an extremely difficult problem.

[Isaac Newton]: We have no people left...

Looking at Newton's messages, Li Dong suddenly noticed a terrifying detail.

[Isaac Newton]: Our world's population is only a little over ten million! And the overwhelming majority of them are concentrated in city-states within the Royal Academy of Sciences' sphere of influence. The world outside remains an uncivilized wilderness!

[Isaac Newton]: As large numbers of farm laborers are transferred into factories, our food production is plummeting! But without enough food to fill those workers' stomachs, those great machines will ultimately become nothing more than heaps of scrap iron!

"Only a little over ten million people?!"

Li Dong stared at those words, secretly alarmed.

This was definitely not the seventeenth-century Earth he knew!

From the sound of it, that world seemed to have no concept of nations at all. It was entirely a "scientific utopia" led by the Royal Academy of Sciences?

"So this is the current state of Universe No. 1666 in a parallel spacetime..."

Li Dong swallowed. Though shocked by the social structure of that other world, the moment food production was mentioned,

he immediately thought of what he had learned in the previous biology class.

So he said in the group chat.

[Currently Grinding Senior-Year Problems]: @Isaac Newton, Sir, I have an immature suggestion regarding food production.

[Currently Grinding Senior-Year Problems]: We can use the "hybrid vigor" between different plant strains to identify specific mutants and establish "male-sterile lines," "maintainer lines," and "restorer lines." As long as these three systems are put into operation and enable the large-scale propagation of superior varieties, doubling food production will absolutely not be a dream!

After Li Dong sent that message, the group suddenly fell silent for five or six seconds.

[Isaac Newton]: ???

[Isaac Newton]: Your Excellency Senior-Year, I have heard of the hybrid vigor you mentioned. Horticulturists can indeed breed stronger crops through crossbreeding, but no one can explain the underlying principles, much less achieve stable, large-scale propagation!

[Isaac Newton]: Even if they can crossbreed, how do they pass this advantage on to the next generation? Do they mix together like fluids? And what sort of absurd concept is this so-called "male-sterile line"?

Newton was completely bewildered.

In Newton's Universe No. 1666, Classical Mechanics might have reached its peak a century ahead of schedule, but biology was probably still in an extremely primitive and ignorant stage.

Looking at Newton's questioning messages, Li Dong was briefly at a loss as well.

Although he had forcibly derived the basic framework of cytoplasmic-nuclear interaction (S-rr) in biology class just now and knew how to solve problems involving it,

knowing how to solve a problem and explaining it to a seventeenth-century physics genius were completely different matters.

Just as Li Dong was wondering how to explain biology to the big shots in simple, understandable terms...

a group member suddenly spoke up.

[That is not absurd, Sir Newton.]

Li Dong froze for a moment, then looked at the person's ID.

[Gregor Johann Mendel]

That man!

The man who had made countless high school students go blind calculating the probabilities of red flowers and white flowers, tall stems and short stems, yellow round seeds and green wrinkled seeds!

The true god of biology—Mendel!