The eighth grade scientific papers are about 1000 words.
Why is the trunk round?
In the process of observing nature, I happened to find that the shape of the trunk is almost a round and empty cone. Why is the trunk conical? What are the benefits of a conical trunk? In order to discuss these problems, I made more in-depth observation and analysis.
With the help of my tutor, I consulted relevant materials and learned that the stems of plants have the functions of supporting plants and transporting water and other nutrients. The stems of trees are mainly composed of vascular bundles. The supporting function of stem is mainly borne by wood fibers in xylem. Although the stems of woody plants will become thicker year by year, in a certain time range, the number of woody fibers in the stems is certain, that is, the cross-sectional area of the stems is certain. Then, based on the assumption that the cross section of the trunk grows into different shapes, we design experiments to explore the reasons and advantages of conical trunk.
Through experiments, we find that when the cross-sectional area and length of (1) are fixed, the vertical supporting force of triangular columnar objects is the largest and the lateral bearing capacity is the smallest; The vertical supporting force of cylindrical objects is not as good as that of triangular cylindrical objects, but the lateral bearing force is the largest; (2) For trunks with the same mass and different shapes, the short conical trunk bears the largest wind force; (3) Wind is a natural phenomenon, which affects the cross-sectional shape and height of trees. The approximate cone-shaped trunk has a low center of gravity, and the huge root system is connected with the earth, so the center of gravity drops lower and the stability is greater; (4) The cross section of the trunk is round, which can reduce the damage, has stronger mechanical strength and can resist the wind attack. At the same time, under the action of the wind, the bending degree of the trunk is similar everywhere. No matter which direction the wind blows, the resistance of the trunk is similar, and the trunk is not easy to be damaged.
The above experiments reflect the laws of nature, and nature enlightens us: (1) A columnar object with a triangular cross section has the greatest vertical supporting force, and its shape can be used in buildings, such as angle steel; (2) A circular object with a circular cross section has the largest lateral bearing capacity, and similar building materials can be found everywhere, such as TV towers and telephone poles.
In the process of observation, experiment and analysis, I gradually explained and revealed the mystery of conical trunk, increased my knowledge, and combined my knowledge with practice, which not only consolidated my knowledge, but also improved my interest in learning, and initially learned the scientific observation and analysis methods.
The eighth grade scientific papers are about 1000 words.
When it comes to essays on science and technology, I recall many small experiments I have done before, and many strange imaginations suddenly appear in my mind. For example, the liquid experiment of aloe brewing medicine has been done; Experiment of thermal expansion and cold contraction. In the future world, can we grow a pair of flying wings? Can fish swim in the sky? Can we invent a machine that won't make our hands and feet calluses? . Wait a minute. In a word, those fantastic ideas and products I have made reappear in my mind, especially the water experiment, which makes me remember vividly.
When I got home, I first picked up a transparent glass and then poured some boiling water into it. I turned on the tap gently and let the water drop by drop. I thought to myself: haha! The first step is so smooth that the next steps will be smooth! Then I opened the green oil bottle and let the oil pour into the cup little by little. Then I stirred them up with chopsticks, and the water and oil gradually merged together, but after a while they separated and became two layers: the first layer was green oil, and the second layer was boiled water; I thought about it: hey! How about I get some soy sauce and see what happens? I bought some soy sauce and put it in a cup, and stirred it. The soy sauce and boiled water melted together, but the green oil was still on the first floor. I thought: What about honey? Then, I took out some honey and mixed it with these liquids. Although they began to mix together, they became three layers after a while: the first layer was green oil, the second layer was soy sauce and soy sauce, and the third layer was honey.
I can't help thinking: Why are different liquids mixed together? I want to confuse people. In order to understand this truth, I took it to my father and asked curiously, Dad, you see, no matter how I stir these liquids, I always keep three layers. Dad looked at these liquids carefully, and then mysteriously said to me, dear daughter, do you think there is any difference in the weight of these liquids?
I held this cup of liquid in front of me, looked at it carefully and thought about it: weight? What is the relationship between liquid and weight? I ran to my father with questions and asked: Are these liquids light or heavy? Dad answered affirmatively: Of course! Dad's affirmative answer suddenly solved the mystery in my heart: Oh! It turns out that the lightest liquid is always at the top, the heavier liquid is at the middle and the heaviest liquid is at the bottom.
Ah! This magical cup of water makes us understand that oil and water are immiscible, and at the same time, it also makes us understand that experiments will make us grow more knowledge and talents.