An unforgettable thing during primary school.

Since I entered primary school, I have taken many classes, including lively Chinese class, interesting math class and endless mysterious nature class. A science class in grade three is still fresh in my memory.

It was a Tuesday morning three years ago, near the school, and Mr. Hong gave us a special assignment, that is, everyone went home to prepare two egg shells. We were all stunned when we heard the teacher assign this homework. Some people speculate that maybe the teacher will let us make it by hand. Some speculate that the teacher may want us to draw eggs; I guess Mr. Hong must let us do the experiment.

Looking at our puzzled look, Mr. Hong gave a "mysterious" smile, as if to say, "The answer will be revealed in the next class."

At the beginning of the class, everyone was anxious for Mr. Hong to solve the mystery quickly. Miss Hong guessed our thoughts and said slowly, "Students, please put the prepared eggshells on the table. We are going to do an experiment with this eggshell. " I was very proud when I heard that I was going to do an experiment. I guessed Mr. Hong's intention.

"Students, look at this eggshell. Is the arched side easy to break or the sunken side? "

The students said in unison, "The concave side is easy to break."

"Why?" No one knows why.

Teacher Hong went on to say, "Please take out the prepared eggshells and let's do an experiment together."

I put the eggshell on the ground, arched my face, raised my pen about 5 cm high on the eggshell, and gently put it down, and the pen touched the eggshell. Alas! The eggshell is safe and sound. I thought: maybe I didn't work hard! Or try again. This time, I just aim the pen tip directly at the arched surface of the eggshell and pound it hard. Strangely, the eggshell is still intact. I looked around and my classmates looked puzzled like me.

Seeing that we were at a loss, Mr. Hong smiled and said, "Students try again with the concave surface of the eggshell and compare their differences."

We turn the eggshell upside down, so that the concave surface of the eggshell faces upwards, and break the eggshell with a pen. It turns out that the concave surface of the eggshell is so fragile.

"Teacher, why is this?" Some students lost their temper and began to ask questions to the teacher.

Teacher Hong conveniently picked up an eggshell on a classmate's desk in the front row and said, "This is the principle of thin shell structure. Because the arch surface of this structure can offset the external force, the structure is stronger. The Great Hall of the People in Beijing and the Sydney Opera House make full use of this principle. Of course, the thin shell principle is everywhere in our daily life. Please ask the students to discover and explore. "

In the past few years, I gradually found that helmets and car windshields ... all come from the thin shell principle, and this class of teacher Hong left me with a lot of thoughts.

A class can be said to be the smallest unit of primary school study and life, because we have many classes every day. But only this class impressed me deeply.

Today, Mr. Tang announced that he would introduce himself in the third class. After the teacher announced, some students jumped three feet high with joy, but some students were a little worried about whether they could speak well. ..... Soon we ushered in the third class. Just as the bell rang, Mr. Tang picked up the chalk and wrote four big words "Introduction" on the blackboard. After the teacher finished writing, he made an opening remark: "I'm glad to be here with my classmates." After all, my classmates don't know my teacher. Now I'll shoot the first shot. My name is Tang Huilan ... "After the teacher finished speaking, the teacher burst into applause. Then 1 contestant Yang Chenqu came to the stage and saw her giving a speech with a speech in her hand. She slurred her words and stepped down in a few words. "Listen, whose voice is so familiar? "Oh, it was my good friend Zhong Yuling." Hello, my name is Zhong Yuling. I come from Class 5(4), and my strong point is soybean oil. Let's talk about my shortcomings first ... "Look, she writes well! One player after another came on stage in an endless stream. Ah! It's my turn What should I do? I can't help feeling nervous. I immediately adjusted my mood and went on stage. Come and listen to my speech: hello everyone! I'm number 34. My name is Zhang Shaoling. Let me introduce myself, so that everyone can know me better. Everyone has advantages and disadvantages, and I am no exception. My shortcoming is that .......... hopes that everyone will get along well in the future. " As soon as my voice fell, I heard the applause of my classmates.

An interesting class ended in laughter. .....