Chapter 23: Chapter 11: A Boring Summer and Angular Momentum (3)
Chen Zhuo took the water bottle and had a sip.
He wasn’t nervous.
Nervousness stemmed from a fear of the unknown, or a worry about one’s own inadequacy.
For him, this was just a formality.
It was like filling out an employment form before starting a new job—tedious, but necessary.
Wearing the backpack with the Black Cat Detective print, he walked into the examination hall.
Examination Hall 30.
The moment he stepped inside, the originally noisy classroom fell silent for a few seconds.
Dozens of pairs of eyes were fixed on him.
It couldn’t be helped; he was too conspicuous.
Surrounded by a group of older kids who were already going through puberty, some even with fuzz on their upper lips, Chen Zhuo, at just over 1.4 meters tall, looked like an elementary schooler who had wandered into the wrong room.
Although, he was, in fact, an elementary schooler.
"Hey kid, are you in the wrong place?"
A boy with a crew cut in the back row couldn’t help but ask.
Chen Zhuo ignored him.
He found his seat number.
Number 09.
He pulled out his chair, stuffed his backpack into the desk’s cubby, and took out his pencil case.
Pencil, eraser, ruler, compass.
He laid them out neatly.
Then he just sat there, back straight, eyes forward, like a young monk in meditation.
The boy with the crew cut, having been snubbed, pursed his lips and said no more.
DING-A-LING—
The bell to start the exam rang.
The language arts section was the same old boring stuff.
Math.
The test papers were handed out.
Chen Zhuo took his and gave it a quick scan.
Two sides of an A3 sheet, packed with questions.
It was indeed a bit harder than an elementary school final exam. It involved some simple middle school algebra concepts and a few logical reasoning problems.
But in essence, it was still just spinning its wheels within the framework of arithmetic.
Chen Zhuo picked up his pencil and got to work.
Fill-in-the-blanks.
"A pool has an inlet pipe that can fill it in 5 hours and an outlet pipe that can drain it in 8 hours..."
Chen Zhuo glanced at it and wrote down the answer directly.
Calculation problems.
Simplification of complex fractions.
Chen Zhuo worked quickly. His hand was steady, and his handwriting was as neat as if it were type-printed.
The feeling of having to wait for his hand to catch up to his mind was excruciatingly boring.
He had to deliberately slow down and make his handwriting a bit neater to avoid losing points for sloppiness.
「Half an hour later.」
He flipped to the last page.
The final, most difficult question.
"As shown in the figure, in the right trapezoid ABCD, a moving point P starts from point A..."
’Moving points again.’
The people who wrote the test seemed to have a special fondness for these problems where points run all over the place.
In elementary school Math Olympiads, this type of problem was considered top-tier in difficulty because it tested dynamic thinking, requiring the student to animate the figure in their mind and analyze it in segments.
’Still boring.’
Chen Zhuo drew a coordinate axis on his scratch paper.
’I don’t even need to use derivatives; this is just a piecewise function’s extremum problem.’
He spent five minutes translating the solution process into language an elementary schooler could use.
"When point P moves to..., the base length is..., the height is..., and the area is..."
After finishing, he moved on to the final bonus question.
The question was very short:
"An observation from daily life: Why is it that when you ride a bicycle, the faster the wheels spin, the less likely the bike is to fall over? Please try to explain why. (There is more than one correct answer.)"
Chen Zhuo paused for a moment when he saw this question.
Chen Zhuo held his pen and thought for about ten seconds.
He wanted to write about the conservation of angular momentum.
He wanted to write about precession.
He wanted to draw that elegant force-body diagram of a gyroscope.
But in the end, he decided against it.
After some thought, he picked up his pen and wrote:
"It’s like when we play with a spinning top. The faster the top spins, the more stable it is.
When a bicycle wheel spins at high speed, it develops a property of wanting to keep its axis of rotation pointed in the same direction.
It’s like a stubborn person. If you push him, he might wobble, but he doesn’t want to fall over; he wants to keep standing and spinning.
The faster the speed, the bigger this ’stubbornness’ becomes, and the harder it is for gravity to pull it down.
So, when it’s fast, it doesn’t fall."
After writing this passage, Chen Zhuo himself found it a little amusing.
’Explaining the cold, hard law of conservation of angular momentum as a ’stubborn streak’... I guess you could call this a true inheritance of Feynman’s vivid teaching methods, right?’
He drew a little sketch next to his answer.
A rapidly spinning wheel, with a few lines next to it to represent that ’stubborn’ force.
That was his answer.
He glanced at the wall clock.
Forty-five minutes remaining.
All around him was the RUSTLE RUSTLE of pencils on paper, occasionally punctuated by frustrated sighs and the vibration of erasers scrubbing desks.
The boy with the crew cut was scratching his head in frustration, the end of his pen chewed to bits.
Chen Zhuo flipped his test paper over, placing it face down on the desk.
He didn’t turn it in early.
He was here to pass the test, not to put on a show.
He closed his eyes and began to review the Chapter of "The Physics Lectures" he had read last night.
The one about the principle of least action.
It was one of the most elegant and profound principles in all of physics.
Light travels in a straight line because that path takes the least time.
Objects move in a way that minimizes action.
The universe is lazy; it always chooses the path of least effort to operate.
Chen Zhuo felt he should follow this principle as well.
English.
For him, it was even less challenging than the language arts section.
It was finally over.
He packed up his stationery, shouldered his backpack, and followed the crowd out of the examination hall.
The sunlight outside was so bright it was hard to keep his eyes open.
Chen Jianguo was standing in the shade of a tree with his bicycle, a towel draped around his neck, anxiously peering toward the entrance.
Seeing Chen Zhuo emerge, he hurried over to meet him.
"How was it? Are you tired? Have some water."
Chen Zhuo took the bottle and drank a mouthful of lukewarm salt water.
"It was fine."
"Were the questions hard?"
Chen Jianguo asked cautiously.
"Not hard," Chen Zhuo said honestly.
"My hand is just sore from all the writing."
"Heh, that’s good, that’s good."
Chen Jianguo didn’t ask any more questions. He knew his son’s personality; if he said it wasn’t hard, then it really wasn’t hard.
"Let’s go, time to go home! Your mom’s making you braised ribs tonight!"
Chen Zhuo hopped onto the back seat of the bicycle.
As they passed the school gate, he glanced back at the entrance to City No.1 Middle School.
There was a red brick building there.
On its roof stood a large motto.
Investigate Things, Extend Knowledge.
The childish games of elementary school were finally about to be a thing of the past.
"Dad."
Chen Zhuo called out.
"Yeah!"
"I want to buy a new chair."
"What’s wrong? Is the chair at home uncomfortable?"
"It’s too short."
Chen Zhuo looked at his father’s broad back in front of him.
"The desk is too high. It’s inconvenient for studying."
"We’ll buy one!"
Chen Jianguo shouted, his voice filled with a bold spirit.
"We’ll get an adjustable one! One of those executive chairs with wheels!"
The clear ring of the bicycle bell sounded once, merging into the clamorous evening traffic.
That year, Chen Zhuo was nine years old.
With the top score in the entire city, he said an early farewell to his childhood.
The droning sounds of reciting "a-o-e," the struggles with "chickens and rabbits in a cage" problems—he cast them all off like mud from the sole of his shoe, leaving them far behind.
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