20 years of teaching

Chapter 92 Ideal Experiment Method

Lin Feifan picked up the glass bell jar and inspected it, and said: "The contact between the glass bell jar and the gas extraction plate is not tight, and after the gas is pumped away, gas has penetrated through the gap."

"Then how to solve this problem?" Fan Qiang asked.

Lin Feifan said: "Coating the bottom of the glass bell jar with petroleum jelly or engine oil can play a good role in sealing."

"Motor oil or Vaseline? Where can I get it at this time?" Fan Qiang opened the drawer, took out a small white porcelain bottle, and handed it to Lin Feifan, "Can I apply this?"

Lin Feifei took a look at the small porcelain bottle and said with a smile: "Whitening cream? Your sister used it? Your sister's skin is so good, there is no need to use this. Tell your sister, it's best not to put these things on your face. Apply it, it will hurt the skin."

Fan Qiang rolled his eyes at Lin Feifei, and said, "It seems that he cares about my sister. Take a closer look, is it for girls? My sister never uses cosmetics."

Lin Feifan read the instructions carefully and found that it was actually a whitening cream for men. He laughed out loud and reached out to touch Fan Qiangbai's dark face. The reason, let me see how thick you are, you can really pretend!"

Fan Qiang turned his head to avoid Lin Feifan's hand, "Go, go, do an experiment quickly and see how it works."

"How much does this bottle cost?" Lin Feifan asked.

"A bottle costs more than 40 yuan."

"It's really expensive. I use it sparingly. It's greasy. It should work well." Lin Feifei unscrewed the bottle cap, dipped some whitening cream with his fingers, and spread it evenly on the bottom of the glass bell jar.

Take a stack of toilet paper, knead it into a fluffy shape, put it on the suction plate, put the adjusted alarm clock, cover the glass bell cover, and apply whitening cream to the joint.

"What are you doing with the toilet paper?" Fan Qiang asked suspiciously.

Lin Feifan explained: "To weaken the effect of sound transmission through the solid below, if foam plastic is used, it will have a better sound insulation effect."

When the alarm clock rang, Lin Feifan used the air pump to pump air out quickly, and the ringing of the alarm clock gradually weakened until the ringing was very quiet.

"Very good!" Lin Feifei was very satisfied with the experimental results.

Then let the gas gradually enter the glass bell jar, and found that the bell sound gradually increased.

"It's done, very successful!" Lin Feifei said with a smile.

"Then it can be deduced that sound cannot travel in a vacuum?" Fan Qiang said with a slight frown.

Lin Feifan said: "If you do this experiment completely and successfully like just now, you can draw the conclusion of the experiment smoothly based on the experimental phenomena."

"But you can still hear the sound at the end of the draw just now." Fan Qiang felt a little too reluctant.

Lin Feifan explained: "Yes, if you need to answer the experimental phenomenon in this experiment, you must emphasize to the students that you must not answer that you can't hear the sound in the end, but can only say that as you gradually draw your air out, the sound will gradually fade away. Weaken, let the gas gradually enter the glass bell, and the sound gradually increases."

"Why?" Fan Qiang was confused.

"Can the air pump exhaust the air in the glass bell jar? No matter how hard it is, there will be a small amount of air in it, and a faint sound can be heard."

Lin Feifan put down the equipment in his hands, and continued: "The students who answered that they couldn't hear the sound must have never done this experiment. The people who gave the exam questions are experts. Differentiate students from experiments. In science, there is no room for falsehoods. Imagination is not acceptable. Only by seeking truth from facts can true knowledge be obtained through practice!"

Fan Qiang nodded again and again, stretched out his thumbs to Lin Feifan, and praised: "You are in the process of teaching, infiltrating the education of humanistic literacy and scientific spirit. It is very good! I want the original version of these words to be conveyed to my students. I There is also a question, this cannot be vacuumed, how can it be concluded that sound cannot travel in a vacuum?"

Lin Feifan smiled and said: "I asked you, you answered, keep pumping, what is the experimental phenomenon?"

"You just said it, and the only answer is that the voice gradually weakened." Fan Qiang said.

"Then continue smoking?"

"The voice is weaker."

"How about continuing to breathe?"

"It's weaker."

"Then what if it's all pumped out and the inside becomes a vacuum?"

"Then there will be no sound."

Lin Feifan smiled and said, "Isn't the conclusion coming?"

Fan Qiang said in surprise: "It went smoothly, but how do you tell the students?"

Lin Feifei said: "Many physical experiments cannot meet the conditions in real life. For example, in this experiment, you can't create a vacuum environment, so you have to follow this step to infer the correct conclusion. This is a research method, and its scientific name is ideal. Experimental method, commonly known as inference method. Galileo used this research method to study how objects move when there is no force."

Fan Qiang frowned and said, "The textbooks didn't mention any of these knowledge."

Lin Feifan said: "I have been exposed to many versions of junior high school physics textbooks, and found that many knowledge that should be taught to students are not mentioned in the books."

"That's not right. Why isn't what should be taught to the students included in the textbooks?" Fan Qiang said angrily.

"The textbook is just a outline, so it needs to be taught by the teacher." Lin Feifei said.

Fan Qiang was suddenly speechless, looking downcast.

Lin Feifei smiled and said: "Don't be discouraged, come on, come on, today I will sort out the knowledge of Chapter 2 for you, and I will focus on telling you what should be explained to students but not in the book."

Fan Qiang opened the closet, took out a bottle of Jianlibao, pulled the tab, and handed it to Lin Feifan.

Lin Feifei punched Fan Qiang, and cursed: "Hey! You are a miser, and you are too realistic. You just took out Jianlibao now. If I don't tell you about Chapter 2 today, will I not take it out?" Is it? Say, what else is in the closet?"

Fan Qiang said with a hippie smile: "Isn't this busy doing scientific research all the time? There are still a lot of snacks in the cabinet, and you can eat them after you finish the lecture."

"It's not too late to talk after eating." Lin Feifei took a sip of Jianlibao, walked over and opened the cabinet door, and saw that the cabinet was full of Jianlibao and various snacks, as well as a can of milk powder.

Picking up a biscuit, unpacking it and stuffing it into his mouth, Lin Feifan said, "Pack some up and take some away later, and your tuition fee will not be charged."

……

Halfway through, the physics class representative of the class taught by Fan Qiang brought homework.

Looking at the pile of homework, Lin Feifan asked: "How many children are there in a class of junior high school in your school?"

Fan Qiang said: "I don't know about the third grade. There are more than 80 students in each class in the second grade. There is almost no room in the classroom. There are only more than 70 students in each class in the first grade."

"Why are there fewer first graders?" Lin Feifan asked.

"This year, the number of students enrolled in the first grade of junior high school is so high that the school had to add two classes. The number of students in the first grade of junior high school is one or two hundred more than the number of students in the second grade of junior high school. I heard..." Fan Qiang paused, and took two more bottles of Jianlibao from the cabinet. "Here, have another bottle,"

Lin Feifan didn't take Jianlibao, and asked coldly, "What did you hear? Tell me."

Fan Qiang opened a bottle of Jianlibao, took a few sips and said, "I heard... I heard that most of the increased children come from the area served by Jinghu Junior High School. Many children don't want to study in Jinghu Junior High School, so they come here Here we come. The leaders of our school said that if things go on like this, Jinghu Junior High School will be withdrawn and merged in less than two years.”

Lin Feifan threw the unopened biscuits on the table with a displeased expression.

"Boom!"

He placed half a bottle of Jianlibao heavily on the table again, and the orange liquid splashed out from the mouth of the bottle and sprinkled on the back of his hand.

(End of this chapter)