Find a friction force of about 1000 words in a high school physics paper.
When an object moves on the surface of another object, there will be a force called friction on the contact surface of the two objects. For example, in daily life, cars move on the road by the friction between tires and the ground. Friction is usually divided into sliding friction, rolling friction and static friction.
We know that the kicked football will stop slowly because of friction. Carpenters use the friction generated by sandpaper and wooden boards to polish wooden boards with sandpaper. Automobile engine transfers kinetic energy to generator to generate electricity through friction with belt; When people wash their hands, their hands rub to wash away the dust on their hands; The rotation of washing machine causes the friction between clothes and water when washing clothes; When eating, teeth rub against food; Wipe the floor with a mop; Wipe the table with a cloth; Rubbing the blackboard with a board will produce friction. In our life, as long as objects are in contact with each other, there is relative motion or a trend of relative motion, friction will be generated.
Two factors affecting the magnitude of friction:
1. Friction is related to the pressure between contact surfaces. When the roughness of the contact surface is constant, the greater the pressure, the greater the friction. In life, we have a common sense, that is, the tire is flat, and it is even more difficult to ride a bicycle.
2. The magnitude of friction is related to the roughness of the contact surface. When the pressure is constant, the rougher the contact surface, the greater the friction.
How to increase friction and reduce friction
1. The coarser the contact surface of an object, the greater the friction. Such as the pattern of soles and tires. When the car is driving on the road, the tire is in contact with the rough asphalt pavement, which will increase the friction. When the car is driving on the road with snow or water, the friction will be reduced. So pay attention to safety in rainy and snowy days.
2. Reduce the roughness between contact surfaces; The fan shaft should be smooth. Refueling the clock can reduce friction and make the time more accurate. In the skating rink, workers often clean the ice surface to make it smooth, which can reduce friction and speed up skating.
What is the tug of war? Many people will say: Of course it is better than which team! Actually, this question is not that simple.
Through the stress analysis of tug-of-war teams, we can know that as long as the pulling force is less than the maximum static friction with the ground, it will not be pulled. Therefore, increasing the friction with the ground has become the key to success. First of all, shoes with concave-convex soles can increase the friction coefficient and increase the friction force; In addition, the heavier the player's weight, the greater the pressure on the ground and the greater the friction. When adults and children tug of war, adults can easily win. The point is that adults are heavier than children.
In addition, in tug-of-war, the outcome depends largely on people's skills. For example, pedaling hard on the ground can exert more pressure on the ground than its own weight in a short time. Another example is that people lean back, using the pull of the other side to increase the pressure on the ground, and so on. Its purpose is to rub the soles of the feet to the maximum extent in order to win the game.
Through the above research and observation, it is concluded that the friction force depends on the pressure of two objects and the roughness of the surface.
Ask GJ, a senior high school physics paper, to introduce you to a more professional place, how about it, hehe. Go to the "90 Generation Writing Network", where the staff level is quite high. Can write all kinds of papers.
First of all, remember that there must be pressure when there is friction, and friction and pressure are perpendicular to each other. Then, there are two kinds of friction: static friction and dynamic friction. The dynamic friction is proportional to the positive pressure, that is, f = μ n, and the static friction is different. The maximum static friction is often greater than the maximum sliding friction, and the direction and magnitude of static friction are uncertain, and most of them appear in equilibrium. Sliding friction is opposite to the direction of motion, and there are two main factors affecting its magnitude, one is the magnitude of positive pressure, and the other is the magnitude of μ, which is determined by the roughness of the contact surface, that is, the materials of the two surfaces in contact.
Under different circumstances, the factors affecting friction are different. The dynamic friction and the maximum static friction are generally determined by the positive pressure between two objects in contact with each other and the materials, surface properties and contact modes of the two objects in contact with each other. But the static friction has nothing to do with the above, it is determined by the resultant force that makes the objects move relatively. In general, the friction has nothing to do with the contact surface, but in fact, the contact surface will affect the magnitude of the positive pressure, that is, when the pressure is constant, the contact surface is large and the positive pressure will increase. At this time, the friction is related to the contact area. It should be noted that in many cases, the pressure is constant, and when the area changes, the pressure also changes inversely. At this time, the area has no effect on the friction force.
1. Friction is related to the pressure between contact surfaces. When the roughness of the contact surface is constant, the greater the pressure, the greater the friction. In life, we have a common sense, that is, the tire is flat, and it is even more difficult to ride a bicycle.
2. The magnitude of friction is related to the roughness of the contact surface. When the pressure is constant, the rougher the contact surface, the greater the friction.
What is the tug of war? Many people will say: Of course it is better than which team! Actually, this question is not that simple.
Through the stress analysis of tug-of-war teams, we can know that as long as the pulling force is less than the maximum static friction with the ground, it will not be pulled. Therefore, increasing the friction with the ground has become the key to success. First of all, shoes with concave-convex soles can increase the friction coefficient and increase the friction force; In addition, the heavier the player's weight, the greater the pressure on the ground and the greater the friction. When adults and children tug of war, adults can easily win. The point is that adults are heavier than children.
In addition, in tug-of-war, the outcome depends largely on people's skills. For example, pedaling hard on the ground can exert more pressure on the ground than its own weight in a short time. Another example is that people lean back, using the pull of the other side to increase the pressure on the ground, and so on. Its purpose is to rub the soles of the feet to the maximum extent in order to win the game.
Search high school physics papers in Baidu Library. Many of them refer to how to write. If you just want to complete the task, you can first Ctrl+c and then Ctrl+v in Baidu library.
: wenku.baidu search? D6 % D0 % CE % EF % C0 % ED & amp； lm = 0 & ampod=0
The paper on energy and momentum is easy to write and can be cut from many angles. The following ideas are for reference only.
One: step by step. First of all, grasp a clue, such as the generation, cause and function of energy and momentum, and the relationship between them. (Logical analysis) The different meanings of energy and momentum in acoustics, optics, relativity and quantum mechanics. (horizontal analysis) and then put forward your own opinions around the clues.
2. Be unconventional: introduce concepts and research methods, make bold guesses, constantly change the angle of your own thinking, from quarks to the universe and black holes, and integrate with contemporary physical conjectures to broaden your thinking.
Help me, I am also a high school physics paper, and the strict format of the paper is almost like this. You can learn from it.
You should pay attention to the fact that if it is an experiment, you must write the principle clearly, then record the analysis data, and finally have the results and discussion. If you quote an article, mark it and write it at the end of the paper. Pay attention to my format. [M] stands for book, [J] stands for magazine.
As long as you start writing, it will come out naturally, which is simpler than writing a composition.
The influence and significance of advanced mathematics on the development of physics
Abstract: This paper mainly studies the mathematics of19th century. Some mathematics and mathematical thoughts in this period are far ahead of contemporary physics. They are of great significance to the development of physics in the 20th century. This paper briefly summarizes some classic examples in the history of physics, and discusses the significance and influence of higher mathematics phenomena on the development of physics.
Keywords: advanced physics of mathematics
Overview: The simultaneity of the development of mathematics and physics.
Second, the progress of mathematics in the development of physics.
2. 1 overview
2.2 Mathematical tools ahead of physics from18th century to19th century
2.2. 1 group theory
Functional theory
2.3 Mathematical model ahead of physics from18th century to19th century
2.3. 1 Non-Euclidean geometric model and relativity
2.3.2 Mathematical Function Chord Theory
2.4 Other issues
2.4. 1 complex function and physics
Third, summary and further discussion.
introduce
(1) the ancient and modern mathematical thoughts, the first volume, the first 1 page.
② Mathematics: Loss of Determinism, page 50.
(3) "Ancient and Modern Mathematical Thoughts" Volume II, page 199.
④ Terrible symmetry, page 140.
⑤ Ancient and Modern Mathematical Thoughts, Volume 4, 160 ~ 16 1 page.
6. Ancient and Modern Mathematical Thoughts, Volume IV, p. 149.
⑦ Strings of the Universe, p. 163 ~ 137.
⑧ A new paradigm of pure mathematics applied to modern physics.
Pet-name ruby Hilbert's mathematical problems, from the translation of the history of mathematics on page 69.
refer to
〔 1〕& lt； Beauty > M- Klein: Mathematics: The Loss of Determinism [M] Hunan Science and Technology Press, 1st Edition, 1997.
[2] Mathematics History Group, Institute of Natural Science History, Chinese Academy of Sciences, Mathematics History Group, Institute of Mathematics, China Academy of Sciences: Translation Collection of Mathematics History [M] Shanghai Science and Technology Publishing House, 198 1 first edition.
[3] Mathematics History Group, Institute of Natural Science History, Chinese Academy of Sciences, and Mathematics History Group, Institute of Mathematics, China Academy of Sciences: "Translation Series of Mathematics History" [M] Shanghai Science and Technology Press, 1985 First Edition.
The junior high school physics test paper is about 3000 words.
Through the study in junior high school, I found that physics is a very broad subject. It first has basic concepts, then explores experiments, and finally applies them to life to explain the phenomena in life. Here are a few examples:
For example, when an object moves on the surface of another object, there will be a force called friction on the contact surface of the two objects. For example, in daily life, cars move on the road by the friction between tires and the ground. Friction is usually divided into sliding friction, rolling friction and static friction.
We know that the kicked football will stop slowly because of friction. Carpenters use the friction generated by sandpaper and wooden boards to polish wooden boards with sandpaper. Automobile engine transfers kinetic energy to generator to generate electricity through friction with belt; When people wash their hands, their hands rub to wash away the dust on their hands; The rotation of washing machine causes the friction between clothes and water when washing clothes; When eating, teeth rub against food; Wipe the floor with a mop; Wipe the table with a cloth; Rubbing the blackboard with a board will produce friction. In our life, as long as objects are in contact with each other, there is relative motion or a trend of relative motion, friction will be generated.
Two factors affecting the magnitude of friction:
1. Friction is related to the pressure between contact surfaces. When the roughness of the contact surface is constant, the greater the pressure, the greater the friction. In life, we have a common sense, that is, the tire is flat, and it is even more difficult to ride a bicycle. 2. The magnitude of friction is related to the roughness of the contact surface. When the pressure is constant, the rougher the contact surface, the greater the friction.
How to increase friction and reduce friction;
1. The coarser the contact surface of an object, the greater the friction. Such as the pattern of soles and tires. When the car is driving on the road, the tire is in contact with the rough asphalt pavement, which will increase the friction. When the car is driving on the road with snow or water, the friction will be reduced. So pay attention to safety in rainy and snowy days. 2. Reduce the roughness between contact surfaces; The fan shaft should be smooth. Refueling the clock can reduce friction and make the time more accurate. In the skating rink, workers often clean the ice surface to make it smooth, which can reduce friction and speed up skating.
What is the tug of war? Many people will say: Of course it is better than which team! Actually, this question is not that simple.
Through the stress analysis of tug-of-war teams, we can know that as long as the pulling force is less than the maximum static friction with the ground, it will not be pulled. Therefore, increasing the friction with the ground has become the key to success. First of all, shoes with concave-convex soles can increase the friction coefficient and increase the friction force; In addition, the heavier the player's weight, the greater the pressure on the ground and the greater the friction. When adults and children tug of war, adults can easily win. The point is that adults are heavier than children.
In addition, in tug-of-war, the outcome depends largely on people's skills. For example, pedaling hard on the ground can exert more pressure on the ground than its own weight in a short time. Another example is that people lean back, using the pull of the other side to increase the pressure on the ground, and so on. Its purpose is to rub the soles of the feet to the maximum extent in order to win the game.
Through the above research and observation, it is concluded that the friction force depends on the pressure of two objects and the roughness of the surface.
For another example, regarding the reflection of light, light is realized by changing the propagation path of light through a plane mirror or other irregular objects.
Principles and laws of light reflection: detailed description in reference books
Application: car rearview mirror, solar cooker, remote control, bicycle taillight.
You can refer to the above two examples and give another example.
This is my experience in learning physics in junior high school, and it may also be an indispensable part of physics learning in senior high school. Believe me, the more you learn physics, the better, and the more you learn, the more interested you are.
Urgent for junior high school physics papers, the number of words is about 2500. You are too picky. Did someone write for you? Otherwise, you can search online, both of which are available.
Junior high school physics thesis, about 500 words, should be original. Physics is a subject based on observation and experiment. In teaching, consciously guide students to contact with real life and analyze physical phenomena; Making use of things around you and doing physics experiments can stimulate students' interest in learning and deepen their experience. This paper introduces a group of physical phenomena and experiments related to eggs.
1, liquid evaporates and absorbs heat.
Experiment: Just boiled eggs are fished out of the pot and taken directly by hand. Although they are hot, they are passable. After a while, the water film on the eggshell dried up and it felt hotter than when it was first caught.
Analysis: Because the newly caught eggshell is attached with a layer of water film, at the beginning, the water film evaporates and absorbs heat, which makes the temperature of the eggshell drop, so it doesn't feel very hot. After some time, the water film evaporated. The heat transferred inside the egg makes the temperature of the eggshell rise again, so it feels hotter.
2. The essence of thermal expansion and cold contraction
Experiment: Soak the boiled eggs in cold water immediately and take them out after cooling completely.
Analysis: First of all, when an egg is soaked in cold water, the eggshell contracts directly when it is cold, while the temperature of the protein drops very little and the contraction is small. At this time, the eggshell is mainly contracted. Secondly, due to the different properties of different substances, when the whole egg is completely cooled, the protein shrinkage rate of loose tissue is greater than that of eggshells, which leads to the separation of eggshells and makes it easier to peel eggshells.
3. Verify the existence of atmospheric pressure
Experiment: Choose a bottle slightly smaller than an egg and heat a layer of sand at the bottom of the bottle. First, light a ball of alcohol cotton and put it in the bottle. Then, block the bottle mouth with the small head of the shelled egg facing down. After the flame went out, the egg was slowly "swallowed" by the bottle into its belly.
Analysis: the burning of alcohol cotton makes the gas in the bottle expand by heating, and some gas is discharged. When the egg blocks the bottle mouth and the flame goes out, the pressure of the gas in the bottle becomes lower than the atmospheric pressure outside the bottle due to the temperature drop. Under the action of atmospheric pressure, eggs with certain elasticity are pressed into the bottle.
4. Floating and sinking phenomenon
Experiment: Immerse an eggshell in a large-caliber glass filled with clear water. After releasing my hand, I found that the egg slowly sank to the bottom of the cup. Take out the eggs and add salt to clear water to prepare a high-concentration salt solution. Then immerse the egg in the salt solution, and after releasing the hand, the egg slowly floats.
Analysis: The ups and downs of an object depend on the relationship between gravity and buoyancy. The volume of an object immersed in a liquid is the volume of the liquid it displaces. According to Archimedes principle, the relationship between object density and liquid density can correspond to the relationship between gravity and buoyancy. Because the density of eggs is slightly higher than that of clear water, when eggs are immersed in clear water, gravity is greater than buoyancy, so eggs will sink. When immersed in salt water, because the density of salt water is greater than that of eggs and gravity is less than buoyancy, eggs will float.
5, inertia, friction and resistance phenomenon
Experiment: Choose a raw egg and a cooked egg with similar appearance and put them on a horizontal table. Rotate them in the same place with the same force. What can spin quickly is cooked eggs, and what stops after a few turns slowly is raw eggs.
Analysis: There is liquid egg white in the shell of raw eggs. When the external force acts on the eggshell and rotates, the egg white remains still due to inertia, so there is friction resistance between it and the eggshell, which makes the whole egg only rotate slowly. The egg white in the cooked egg has solidified into protein, and the whole egg can rotate quickly when it rotates under the action of external force.
6, the stable balance of the object
Experiment: Choose a raw egg, open a hole at the end of the small head, and clean the egg white and yolk in the eggshell. Slide the weight along the hole. Take the big end of the eggshell as the bottom and hold the eggshell. Light a candle, drip candle oil, and seal the heavy object at the bottom of the eggshell. Candle oil can be sealed to about a quarter of the height of the whole eggshell. After the prepared eggshell is pushed down, the eggshell can stand up automatically. Be a "tumbler".
Analysis: The weight of the seal at the bottom of the empty eggshell and candle oil make the center of gravity of the whole egg close to the bottom of the eggshell. The lower the center of gravity, the better the stability. When the eggshell tilts away from the equilibrium position, the center of gravity of the egg rises. Because the bottom of the eggshell is spherical, the egg body returns to its original equilibrium position under its own gravity.
7, molecular movement phenomenon
Experiment: A salted egg can be made by burying an egg with a complete shell in salt for a period of time. Although the eggshell is still intact, even the yolk inside has become salty.
Analysis: Because there are gaps between the molecules of the substance, the molecules keep moving irregularly, and the salt molecules diffuse into the egg yolk, making the egg yolk salty.
Education Resource Network has collected a group of physical phenomena and experiments related to eggs.