I Just Want to Be a Quiet Top Student

Laboratory building, the entrance to the back door of Physics Laboratory No. 1.

Shen Qi stood outside the back door, observing secretly through the glass embedded in the door.

In the physics laboratory, the heads of scientists such as Newton, Kepler, Faraday, and Watt hang on the walls, and four large characters hang above the blackboard: Unity of knowledge and action.

The layout of the laboratory is different from that of the classrooms in the teaching building. The desks are replaced by long experimental benches. More than a dozen students sit behind the experimental benches. Some instruments and props are placed on each experimental bench. Crash test instruments, timers, heavy hammers, etc.

But no one operated any experimental equipment. The students either rested their chins or frowned, staring at the blackboard in front of them, with pens and paper in front of them.

A schematic diagram of water waves was drawn on the blackboard, and it was written in chalk:

Strictly speaking, water waves are not simple transverse waves or longitudinal waves, because the water motion on the surface is neither perpendicular to the wave velocity direction nor parallel to the wave velocity direction, but the superposition of the two.

When the water is deep enough, each point on the surface makes a circular motion in situ. Let the amplitude be A, the wavelength be λ, and the period be T.

Assuming that A\u003c\u003cλ, what is seen in the reference frame moving with the waveform is a steady flow velocity, then what are the flow velocities at the highest point and the lowest point of the wave?

Without considering surface tension and friction loss, assuming that the density of water is ρ and the acceleration of gravity is g, and considering energy conservation, please prove that the wavelength and period satisfy the relationship: λ=gT^2/2π.

Obviously, what was written on the blackboard was a physics problem.

The physics questions are quite long-winded, and there are a lot of babbling text descriptions.

The first question is not difficult. The flow velocity u-v and u+v at the highest point and the lowest point have been written on the blackboard.

A proof for the second question has not yet been written.

On one side of the blackboard, a young woman was standing by the window. She was wearing rimless glasses, with one hand resting on the window sill, looking out of the window.

Shen Qi, who was secretly watching from the back door of the classroom, made a preliminary judgment. This woman should be the teacher of the Wujing team, and a dozen students including Lin Xingyu are members. The female teacher gave a physics problem for the team members to do. Is this what Lin Xingyu called training?

In Shen Qi's impression, competitions in physics, chemistry, and biology should include experiments. What is the difference between purely doing questions and math competitions? It's just that the topic is different.

Shen Qi continued to observe secretly, the female teacher leading the Wujing team is not very old, she can be between 25 and 35 years old, female teachers leading the Wujing team are rare, let's see how strong she is.

The female teacher turned to face the players in the audience, and snapped her fingers crisply: Who will write the proof process of the second question?

Lin Xingyu raised his hand.

Okay, Lin Xingyu is on stage to prove it. The female teacher said.

Lin Xingyu came to the stage and wrote out the proof process with chalk:

1/2△mv1^2+△mg2A+p0△V=1/2△mv2^2+p0△V

Simplified:

λ=gT^2/2π

proved

After Lin Xingyu finished writing, he looked at the female teacher.

Snapped.

The female teacher snapped her fingers again: Smart.

Lin Xingyu was greatly encouraged: Thank you, Teacher Mu, for your affirmation.

Oh, Mr. Mu. Shen Qi learned the surname of the female teacher of the Wujing team. Where did this teacher Mu come from? Why didn't I remember it? After thinking about it, I have competed in several competitions at home and abroad for more than half a year, and went to the Yanda Golden Autumn Camp for training. I haven’t been to the school very much recently. It is normal for there to be personnel changes in the school.

Lin Xingyu happily returned to his seat, and looked at Teacher Mu with admiration. He had the same expression when he saw Shen Qi just now.

At first glance, Teacher Mu is a learned person. She wears glasses and has short hair. Then she asked another question:

There is a submarine that uses electromagnetic propulsion instead of a propeller, and water flows through the propulsion pipeline without considering the viscous resistance between the water flow in the pipeline and the pipe wall and water.

There is a cuboid area in the pipe, the cross-sectional area of ​​this area is the same as the water inlet, and the size is a×b×c, in which a stable magnetic field B is generated by the superconducting magnet, along the b direction, there is a piece on the upper and lower sides a × b size electrode, into a DC power supply.

Assuming that the current only exists in this cuboid area and is uniform, the steady-state current is I, the seawater density is ρ1, and the seawater resistance is ρ.

Assume that after the steady flow, the inlet pressure of the submarine is p1, the outlet pressure is p2, the area of ​​the inlet is S1=b×c, and the area of ​​the outlet is s2.

1. After calculating the steady flow, take the submarine as the reference frame, the flow velocity v1 and v2 at the inlet and outlet.

2. Calculate the power of the DC power supply after the steady flow.

Teacher Mu's chalk font is strong and powerful, and her hands are fast. She finally drew a schematic diagram of the structure of the submarine propeller, and the question was completed.

I adapted this question based on the physics test questions of a certain year's college entrance examination in eastern Zhejiang Province. I will give you 10 minutes to think and draft. After Mr. Mu finished speaking, he walked towards the front door of No. 1 physics laboratory.

Shen Qi is reviewing the questions outside the back door. This question is not difficult, but there are many physics knowledge points that need to be comprehensively applied. Electricity, electromagnetism, mechanics, energy and momentum have to be combined. Use pure high school physics knowledge to solve the problem. There is no problem with this question.

For most people, high school career is the most knowledgeable stage in their life. They have good memory, quick response, and quick thinking. It is not uncommon to see little princes of all kinds of knowledge and little queens of problem solving.

There are generally two trends after high school, becoming more knowledgeable and cutting-edge, or tending to be mediocre.

Less of the former, more of the latter.

Youth is short and precious.

Why not pretend to be young.

After passing this village, there is no such shop.

Time is not forgiving, pretending to fight for the day and night.

The characteristic of physics problems is that thinking dominates everything, supplemented by necessary calculations. In terms of calculation volume, most branches of physics cannot be compared with mathematics.

However, it is difficult to make a difference in physics only by relying on pure mathematical calculation ability without understanding the many formulas and principles of physics. Ouye's kind of calculation Ji can only major in mathematics, while Shen Qi can double Xiu.

In a very short period of time, Shen Qi had mentally calculated the first question of the submarine problem, and the amount of calculation was not large.

At this time, Teacher Mu came out from the front door of the physics laboratory. As soon as she went out, she found a sneaky boy outside the back door peeking into the laboratory.

Teacher Mu didn't show any signs of expression. She went downstairs from the corridor near the front door, went up to the third floor after reaching the end of the second floor, and walked back slowly behind Shen Qi.

Shen Qi, who was concentrating on the second question of the submarine problem, did not notice that there was a female teacher standing behind him.

Interesting? Teacher Mu said softly behind Shen Qi.

It's not interesting... eh? Shen Qi turned his head suddenly, what the hell, is this Teacher Mu a ghost? Why is there no sound when walking?

Teacher Mu looked at Shen Qi carefully, and said after a while: Shen Qi, the IMO perfect score champion, why did you eavesdrop on my physics class?

Mr. Mu, hello, I'm just passing by. Shen Qi quickly regained his composure.