In the cold winter, when I get up in the morning, I often see beautiful ice flowers on the window glass. Some are like orchids, some are like masson pine, crystal clear and beautiful! Who on earth painted such a beautiful pattern on the window glass?
Who else is so clever besides nature?
Ice is no stranger to us, and the relationship between the shape of ice and its formation process may be ignored by most people. The ice in the water is often pieces, and you can't see any characteristics. That's because water molecules are densely distributed. When a large amount of water freezes, the ice crystals are intertwined, so there is no regularity. The falling snowflake is hexagonal because the water molecules of water vapor in the air are not subjected to uneven external pressure during condensation, and the ice crystals have formed unique shapes due to their own crystal characteristics. In fact, the ice crystals in a large block of ice are actually hexagonal, but we can't see them because they are intertwined.
The ice flowers on the window glass are formed because the water vapor in the air meets the sublimation of cold glass, and most of them are hexagonal. The reason why different patterns are formed is the difference of some environmental factors such as the formation of ice crystals. After ice crystals are formed, they will gradually develop around. At this time, many factors will affect the pattern of ice flowers, such as different air velocity on the surface, different roughness of the glass surface, different temperature changes and so on. The ice flowers on the glass vary in thickness, but the thinner parts will melt after a little heating and solidify after cooling, thus forming various patterns.
There are many similar seemingly magical and interesting physical phenomena in our life. In fact, as long as you carefully observe, think and explore, it is not difficult to find the mystery!
The mystery of lever
Archimedes once said, "If you give me a fulcrum, I can move the earth."
What is the fulcrum? Can you have such great power? The concept of lever is introduced. What is a lever?
The ancient Mohist school in China accurately expounded the lever in the Mohist Classic: "The balance of wood is unshakable; Scratching the rope on the right school is extremely heavy. " It means: adding an object to one end of the lever can't make it rotate because the other end is pressed by a heavy object; When the fulcrum moves close to one end of the heavy object, the lever can move at the other end even if there is no object to pry the heavy object. It can be seen that with a small force acting on the lever, a large force can be obtained. The same is true of Archimedes' story about the earth shaking.
Let's look at another interesting experiment: the equipment to be prepared is: a hard wire, two carrots, a soft water plug, two needles, a glass and a candle. Put these things in the picture below and move two carrots until the wire is horizontal. Then light a candle and burn one end of the wire. After burning for a period of time, one end of the burning will sink and the other end will tilt. Why is this happening? Because the heated end of the wire will expand, the length will become longer, the arm of the lever will become longer, but the force will not change, and the product of the force and the arm will become larger, so the burnt end will fall off.
Understanding leverage is to use leverage, which is scientific. For the application of leverage, our ancestors of the Chinese nation can be said to be the first. This can be traced back to the Spring and Autumn Period. Zi Gong, a disciple of Confucius, once passed Hanyang and saw an old man carrying a clay pot to carry water to water the vegetable fields. It took him a long time to water a small vegetable field. Zi Gong said to the old man, "There is a machine called' orange', which has a simple structure. Build a shelf with wood, put a crossbar on it and hang a bucket at the front end of the crossbar. Put it on this well, and use the principle of putting more emphasis on the rear than on the front, and you can draw water from the well without much effort. This machine can water hundreds of beds a day, which is much better than your current method. " The "orange jar" introduced by Zigong is a kind of lever, which uses an upright shelf to frame a crossbar with a fulcrum in the middle, a bucket hanging at the front end and a heavy object hanging at the back. When people put the bucket into the well and fill it with water, they can easily lift the bucket out of the well with the help of gravity at the back end of the crossbar. This simple machine has been used for more than 2000 years and can still be seen today.
Lever is ubiquitous in life and plays an important role in people's body. Let's look at our muscles. If you can lift the weight of 100 cows, is 100 cows your strength? Then you are wrong. Your arms are much stronger than this. Like biceps brachii. This muscle is fixed near the fulcrum of the forearm bone lever, and the weight acts on the other end of this lever. The distance from the weight to the fulcrum (joint point) is about 8 times that from the end of biceps brachii to the fulcrum. Therefore, if the weight lifting is 100 N, then the tension of the muscles on the forearm should be 800 N, and the strength of the muscles is 8 times that of the arms. Therefore, a person's strength is much stronger than he shows. In other words, our muscles are more powerful than our daily performance.
At this point, the article should be over. But ... if you think about it, you will find something new. As mentioned above, it seems that the arm structure of human beings seems unreasonable, and it is laborious to work, but whatever is laborious should save the distance, so our movement speed will be accelerated, which ensures the flexibility of limbs, is more reasonable than strength, and is easier to survive in the crisis of nature.