Why do needles float on the water essay 600 words

Can a needle float on water? Could it be that the needle will "backstroke"?

During the summer vacation, I read an interesting science experiment book called "Science and Technology Activities", and the first article caught my eye, "Little Experiment --- Needle Floating on Water".

We have needles in every household, but how can it float on water? I was so curious that I couldn't wait to read on. Lab supplies are very easy to find, just a needle, a bowl of water and a fork are all you need.

Next, I will do the experiment, and interested students can also try it with me.

First, I prepare lab supplies, a needle, a fork, and a bowl full of water. I picked a large bowl because swimming experience has taught me that the deeper the water, the more buoyant it is.

In the first step, drag the needle with a fork and carefully lower it to the surface of the water. This step, I held my breath and did it carefully ......, don't look at such a small action, the white hair and sweat on my head come out. I don't know if my hands were excited or nervous, some of them were not very obedient, and the hand holding the fork trembled slightly, and it was really not easy to do such a careful flat action.

Note that going down again is a crucial step in determining success or failure.

The second step is to slowly remove the fork and the needle will float on the water. When removing the fork, you must be slow and do not tremble your hands, or you will lose all your efforts. The needle floating on the surface of the water is so interesting, it is like learning to swim backstroke, and it just lies flat in a bowl full of water and ...... quietly

Isn't it amazing? So why is that?

I continued to look for the answer in the book, and it turned out to be tension! The surface tension of the water supports the needle, and the needle does not sink. The tension on this surface is the cohesive connection formed by the water molecules.

The tension is amazing! Students, did you get a backstroke needle like me?

In fact, this is also a matter of common sense、You can start writing from life, first you can write an inscription, determine what you are writing, because the size of the needle is smaller, the area of water is large, and the bearing capacity is large, so the needle will float on the surface of the water。

The surface tension of the water supports the needle so that it does not sink. Surface tension is the cohesive connection formed by water molecules. This cohesive connection is due to the fact that a certain part of the molecules is attracted together, and the molecules are squeezed against each other to form a thin film.

This layer of film is called surface tension, and it holds objects that are supposed to sink.

Psychology is a science that studies human psychological phenomena, mental functions, and behaviors. It includes two major fields: basic psychology and applied psychology. Basic psychology research involves perception, cognition, emotion, personality, behavior, interpersonal relationships, social relations, family, education, health, society, etc.

Psychologists engage in basic research with the aim of describing, explaining, **, and influencing behavior. Improving the quality of human life, Meaning of Psychological Symbols: Symbols mean soul in Greek, which later became English psyche.

Applied psychology attempts to explain the basic behavior and psychological functions of individuals with the operation of the brain, and the role of individual psychological functions in social behavior and social dynamics is related to neuroscience, medicine, biology, etc.

The word psychology is a Greek word that means the science of the soul. The soul also means gas or breath in Greek, because ancient people believed that life depended on breathing, and when breathing stopped, life ended.

With the development of science, the object of psychology changed from the soul to the mind. It was not until the beginning of the 19th century that the German philosopher and educationalist Hurlbut first proposed psychology as a science.

Originally, psychology and education both belonged to the category of philosophy, and later they were separated from the infancy of philosophy. Scientific psychology not only describes psychological phenomena, but more importantly, explains psychological phenomena in order to reveal the laws of their occurrence and development.

Psychology is a science that studies the psychological phenomena, mental functions and behaviors of humans and animals, and is both a theoretical and an applied discipline. It includes two major fields: theoretical psychology and applied psychology.

The study of psychology involves many areas such as perception, cognition, emotion, personality, behavior, and interpersonal relationships, and is also related to many areas of daily life – family, education, health, etc.

On the one hand, psychology tries to explain the basic behavior and psychological function of individuals by using the operation of the brain, and at the same time, psychology also tries to explain the role of individual psychological functions in social behavior and social dynamics. At the same time, it is also related to neuroscience, medicine, biology and other sciences, because the physiological effects of these sciences affect the individual's mind.

To put it simply, neuroscience research studies the psychology of human brains by looking at their reactions; Developmental psychology is the study of how humans grow, develop, and learn;

Cognitive psychology is the study of psychology through computer methods, that is, the psychology is compared to a computer, to see how human beings play, distinguish language and object recognition, etc.; Social psychology is the study of human group behavior and how to communicate with others; Clinical psychology focuses on mental health and mental illness. Psychology is mainly a course that helps people with their mental health.

Physically, the density of water is 1 g m, and the density of the needle is twice that of it, so from this point of view, the needle should also sink to the bottom. But the needle can float on the water. Generally, objects float on the surface of the water by the buoyancy of the water.

The needle is different, the needle can float on the surface of the water by the surface tension of the water. When we put the cork in the water, we see that it is partially immersed in the water and part on the water, and this is the role of buoyancy. And put the needle in the water, in fact, it is not immersed in the water at all.

We can see a groove under the needle, which is formed by the surface tension of the water, which holds the needle up.

The tensile force that interacts between any two adjacent parts of a liquid surface perpendicular to their unit length demarcation line. The formation of surface tension is closely related to the special stress state of the molecules in the thin layer of the liquid surface. The presence of surface tension creates a series of special phenomena that can be observed in everyday life.

For example, capillary phenomena in thin tubes with very small cross-sections, soap bubbles, wetting and non-wetting between liquids and solids, etc.

When the water molecules are close together, there will be a mutual attraction, but the water molecules on the water surface, there are no water molecules in the air above, and they can only attract each other with the water molecules under the water, forming a resultant force pointing inward on the surface, which is the surface tension of water.

At room temperature (around 20), the surface tension of most liquids is in the range of 20 40 dynes, but there are also those that are greater, such as the surface tension of water is 72 dynes.

Do you know why needles float on the water?

The surface tension of the water seems to cover the surface of the water with an invisible "film", and it is precisely because of this "film" that the paper clip is "lifted" on the surface of the water without sinking to the bottom. In addition, the surface tension gives the surface a tendency to keep the surface area to a minimum, so that all the paper clips are pressed together.

In fact, the needle can float on the surface of the water, mainly because the water has a certain surface tension. When we gently place a needle or a coin that we think will sink to the bottom of the water, we will see that the surface of the water will sink a part, and the sunken water surface will generate an upward force to support the needle or coin so that it does not sink to the bottom. Therefore, in ancient times, girls would use this method to see whose embroidery needle could float on the surface of the water on the night of Qixi Festival.

Because they don't dissolve in water, they stick to the needle tightly and squeeze some of the water out of it.

If you throw a sewing needle into the water, it will sink to the bottom. If you carefully lay it flat on the water, you will find that the needle will float smoothly on the water. In fact, this is because the surface tension of water is at work, and various liquids form something like a tense rubber film on the surface because of the strong force on the surface, and the same is true for water, so things placed on the surface of the water, as long as they do not crush this surface, can be held up by a rubber film.

If you look closely, the water surface is concave around the needle, which means that the needle is sinking due to gravity, but the tensioned water surface is holding it, so the needle is floating on the water. If you rub the needle on your nose or hair for a while to give it an oily film, it will be easier to float on the water.

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