In the process of observing nature, I happened to find that the shape of the trunk is almost round-an 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.

Fan Wen 2: Why do leather shoes shine brighter and brighter?

Every Sunday, I always finish the task of shoeshine given to me by my mother. Tell you, this is the source of my pocket money for a week! After getting the leather shoes covered with dust, I first wipe off the dust on the vamp, then apply shoe polish and wipe them carefully, and the leather shoes will become bright and beautiful. But why is this?

I found two pairs of old and new leather shoes of the same brand and style for comparative observation. I first touched the uppers of two pairs of leather shoes and found that the surface of the new shoes was much smoother than the old ones. Old leather shoes are coated with shoe polish. After careful polishing, it shines a lot, but it is still not as good as new leather shoes. Is there a relationship between the brightness of leather shoes and the smoothness of uppers?

I brought a pair of old leather shoes that were not polished, and the uppers were uneven under the magnifying glass. Then, I circled two rough areas A and B on the leather shoes. Carefully wipe area A with shoe polish, and area B without shoe polish as a blank control. I found that the surface of area A is obviously smoother after wiping, and it is more shiny than area B when placed in the sun. Why is there such a big difference between them?

I think the teacher once said in physics class that the wall of the theater is uneven, so that most of the sound can be absorbed and the audience will not be disturbed by the echo. Similarly, light will be reflected on the surface of any object. If the plane is uneven, light will scatter in all directions. If this plane is smooth, then we can see the reflected light in a certain direction.

The surface of leather shoes is not absolutely smooth. If it is an old leather shoe, its surface is of course more uneven and can't reflect light in a certain direction, so it looks dull. There are some small particles in shoe polish, which can just be filled into the pits on the surface of leather shoes when shining shoes. If you wipe it with a cloth again, the shoe polish will be more uniform, the surface of leather shoes will become smooth and flat, and the reflective ability will be strengthened.

Through the experiment, I finally know the secret of shoes getting brighter and brighter!

Model essay 3: What effect does vinegar have on flowers?

Vinegar is a common condiment in life, while flowers can purify the ecological environment and beautify our life.

Have you ever thought about the relationship between vinegar and flowers? We explored the subject with curiosity. According to people who have rich experience in planting flowers, applying some vinegar on potted flowers can improve the growth of potted flowers and increase flowers, which are bright and leafy. We soon confirmed this in the experiment.

Do different concentrations of vinegar have different effects on flowers? This is the second stage of our experiment. We select four pots of gypsophila paniculata, primrose and Chinese rose with the same growth and divide them into four groups. Each group (three pots) has three kinds of flowers, which are numbered and labeled respectively. At the same time, we prepared edible white vinegar into three solutions with different concentrations: 1% (pH 2~3), 0.0 1% (pH ≈4) and 0.000 1% (pH ≈6), and sprayed vinegar on three groups of potted flowers once a day, while the fourth group did not. Observe and record the growth of flowers every five days.

The results of this experiment are as follows: spraying low concentration vinegar (pH ≈6) has no obvious effect on these flowers; The flowers sprayed with moderate concentration of vinegar (pH ≈4) are obviously better than other groups, with more buds, earlier flowering, richer colors and longer flowering period. Spraying high concentration vinegar with pH value of 2-3 will make the flowers wither prematurely.

Through this experiment, we can tell you that spraying vinegar properly when planting flowers can make flowers grow better. But to master the concentration of vinegar, excessive acetic acid will harm flowers.