pjbooks Chapter 20: The Physics Teacher's Test
Chapter 20: The Physics Teacher's Test
Ever since he learned that a math competition prodigy had emerged from Class 09 and was favored by Cao Wen, Fang Jianyu had been feeling a pang of jealousy and a desire to "piggyback" on his success.
After all, to be honest, Han Chuan's math score improved from 67 to 93 in two months, but that improvement wasn't as dramatic as his physics score, which went from 51 to 91.
This steep upward curve was unprecedented in his many years of teaching experience.
What does this tell us?
This shows that this student's talent in physics far surpasses that in mathematics!
Such a promising physics student has no reason to pursue math competitions instead of physics competitions!
If we can get Han Chuan into the physics competition team, maybe the school can make a breakthrough in the provincial physics competition this year, and he, as the physics teacher, will also be proud!
So much so that in the following days, when Fang Jianyu was teaching in Class 09, he couldn't help but glance at the window seat in the back row, observing Han Chuan.
After all, if you're going to recommend someone to participate in a competition, a physics score of 91 is definitely not enough.
He needs to learn more about Han Chuan to see if he is truly talented or just lucky, achieving his results by doing a lot of practice problems.
After observing the student for the past few days, Fang Jianyu was somewhat surprised to find that the student neither answered questions prematurely nor acted arrogantly during class.
He didn't listen to the lectures most of the time; instead, he would often doodle on draft paper, as if he were learning on his own.
"Is he truly gifted, or just a 'pseudo-genius' who only knows how to cram for exams?"
In class, seeing that Han Chuan wasn't paying much attention, Fang Jianyu decided to give him a try. It just so happened that the lesson was about the motion of charged particles in a magnetic field in a composite field.
This section combines mechanics and electromagnetism, and is recognized as one of the most challenging topics in high school physics. It is also the knowledge that most often appears in the final questions of the college entrance examination.
Thinking it over, he picked up a brand new piece of chalk from the chalk box, broke off a small section, and then drew a huge three-dimensional coordinate system on the blackboard with a wave of his hand.
The chalk glides rapidly across the blackboard, making a "scratching" sound, and the x, y, and z axes intersect and extend, constructing an abstract spatial cage.
Magnetic field lines, electric field lines, gravity arrows... all sorts of chalk lines are densely stacked together, making one dizzy just by looking at them.
After drawing the diagram, he immediately added the question to the blackboard.
As shown in the figure (a huge three-dimensional coordinate diagram), in the spatial rectangular coordinate system O-XYZ, there exists a cylindrical composite field region with height H and base radius R.
[This region contains a uniform electric field (directed along the negative z-axis with magnitude E), a uniform magnetic field (directed along the positive z-axis with magnitude B), and a gravitational field (which can be considered a uniform gravitational field directed along the negative z-axis with g acceleration).]
A small ball (which can be considered a point mass) with mass m and positive charge q is released from rest at point P, which is directly above the center O of the bottom surface of a cylinder and at a height h0 (h0 > H) above the bottom surface.
[...Find the stable range and period of motion of the ball along the z-axis within the cylindrical region.]
After finishing writing the question, Fang Jianyu tapped the blackboard, glanced around the classroom, and began to speak.
"I took this question from the previous physics competition semi-finals. The college entrance examination will not test this level of difficult questions, but it can be used to practice thinking."
"Anyone want to come up and give it a try?"
Upon hearing this, the classroom fell silent.
Apart from a few top students in the front row who dared to stare at the blackboard and try to organize their thoughts, everyone else lowered their heads, afraid that Teacher Fang would call their names.
The questions were from a competition, and they were even more difficult than those in the college entrance exam. This was completely beyond their capabilities.
Even the top students who had good physics scores were frowning, and none of them dared to raise their hands and speak up.
"Han Chuan".
Seeing no movement in the classroom, Fang Jianyu's lips curled into a smile. He looked at the student in the middle and back rows who was still immersed in his own world and called out to him.
"You give it a try!"
Beside him, Li Hao, Han Chuan's deskmate, nudged him as he worked on his worksheets and whispered, "Brother Chuan, the teacher is calling you."
"oh."
Han Chuan responded, put down his pen, stood up, and walked onto the podium.
He paused for a moment as soon as the question on the blackboard came into view.
This question.....
It seems to be very similar to the problems he's been working on lately; they're both complex problems combining mechanics and electromagnetism. Zhou Peiyuan has been teaching him these things these past few days.
Han Chuan became engrossed in the questions on the blackboard without realizing it.
Suddenly, a silvery-blue light quietly rose from the edge of his consciousness, gently isolating the entire classroom from all other sounds and sights like a tide.
The two-dimensional diagram on the blackboard suddenly disintegrated and reconstructed in his vision, instantly expanding into a real, three-dimensional, and dynamically operating physical world!
The ability to visualize knowledge was activated at this moment.
The ball on the blackboard is no longer a circle as shown in the diagram, but a real, rotating metal ball.
It is released from rest at the top of the insulating slope, and the gravitational potential energy is transformed into a golden halo flowing downwards, driving it to accelerate.
The moment the ball entered the region of superposition of electromagnetic fields, the whole world lit up!
The vertically downward gravity line is a steady dark gold color, which together with the silver light filaments supporting the inclined plane weaves the first layer of motion trajectory.
Immediately afterwards, the horizontal uniform electric field lines, a dazzling purple, split the positive charge carried by the small ball, generating a constant deflection force.
But the most magnificent thing is the magnetic field! Countless closed magnetic field lines fill the entire space...
Gravity, electric force, and Lorentz force—three completely different forces—act simultaneously, superimpose, and counteract each other on the small ball, each with a distinct color and form!
The trajectory of the ball is no longer a pre-set parabola, but a band of light that twists in three-dimensional space!
At this moment, the sense of time is stretched to its limit.
What Han Chuan saw was no longer Newton's laws and kinematic formulas, but the most essential and intuitive picture of force and motion.
Lorentzin's characteristic of "never doing work, only changing direction" is vividly demonstrated in this dynamic scene.
Each pulse precisely cuts in the direction of velocity, only causing the trajectory to curve, but never changing the ball's kinetic energy.
He didn't know how much time had passed when his physics teacher's voice rang in his ears again.
"How's it going? Any ideas?"
All eyes in the class turned to Han Chuan again, filled with curiosity and sympathy.
After all, most of the students in the class believed that Han Chuan would definitely not be able to solve the difficult competition problems that were not even on the college entrance examination.
Coming to his senses, Han Chuan nodded and said, "I have a little bit of an idea."
.....
PS: Second update! Please read on, and vote with monthly tickets and recommendations!