Xijiao School, Zhucheng City, Shandong Province (262200) Dong Guorong Song Xinyong hangs a heavy object (not reacting with the solution). If the cerium hydroxide is gradually added to the copper sulphate solution until it is completely reacted, the indication of the spring balance will be filled. ", "small" or "not heavy objects except for the vertical downward gravity, the buoyancy of the solution to its vertical upwards and the tension of the spring scale; the spring balance reading is equal to the gravity of the f minus the weight The buoyancy, because the two solvents produced the following reaction with 02+!- +, the two kinds of sinking factors formed exactly the reaction, so the liquid j in the beaker left the solvent water. Because the density of water is less than the copper sulfate solution The density, the buoyancy of the weight is reduced, so the display of the spring scale becomes larger.
An iron block is hung and immersed in a beaker containing CuS04 solution. After a period of time, how the spring balance will change, the weight is similar, and it is also subjected to gravity, solution to its vertical upward buoyancy and spring balance. Tensile force; due to iron ball and CuS04 solution = Cu + FeS04) - copper precipitates on the iron ball after a period of time, which makes the mass of the iron ball increase, and the mass of the solution decreases * the density of the solution decreases - iron ball The buoyancy received is reduced (the change in ball volume is negligible), so the display of the spring balance becomes larger.
Example 3: The beaker contained in the beaker is a barium hydroxide solution. When the switch S is closed, any one of each group of solutions is added to the barium hydroxide solution to make the display of the spring balance smaller and then change. Large in cesium hydroxide. The solution should be added to the solution () hydrochloric acid and dilute acid dilute sulfuric acid and H2C03. It is known from the title that if the indication of the spring scale is first reduced and then enlarged, the magnetism of the electromagnet must be weakened first. Strongening - According to the analysis of the factors affecting the magnetic strength of the electromagnet, it is known that the magnetic strength of the electromagnet is only related to the current intensity through the solenoid when the number of solenoid turns is constant and there is a core. The strength of the current in the circuit is determined by the conductivity of the solution, and the conductivity of the solution depends on the ion concentration of the freely moving solution in the solution. The greater the ion concentration, the stronger the conductivity, and vice versa, the conductivity of the solution becomes weak. The added reagent should have the conditions that can react with the cesium hydroxide solution and the resulting product is difficult to ionize. * The solution in (A), (C), (D) and the cesium hydroxide solution react to form BaCl2, NaOH, Ba, respectively. (no3) 2, etc., which can ionize the ion, and the conductivity in the title becomes weaker and then becomes stronger. Only when any one of the solutions of the group (B) is added, the sulfuric acid which is hardly soluble in water is produced. Earthworms, barium carbonate and hardly ionized water, Therefore, with the addition of dilute sulfuric acid or carbonic acid, the number of ions in the solution decreases, and the conductivity gradually decreases; when the two react completely, the conductivity is the weakest; when dilute sulfuric acid or carbonic acid is added, the H+, sr or The cr ions gradually increased, and the conductivity began to increase. Therefore, when only one of dilute sulfuric acid and carbonic acid is added, the display of the spring balance will be smaller first and then larger.
Comments: The above three questions are the physical and chemical comprehensive questions based on the change of the spring scale. In order to solve such exercises smoothly, it is necessary not only to master the chemical knowledge such as the reaction law between acid, alkali and salt solution and the law of metal displacement reaction; but also to master and flexibly apply the relationship between buoyancy and liquid density of objects. And the knowledge of the force analysis of the object and the factors affecting the magnetic strength of the electromagnet.
(3rd) Preparing for strength and gravity æ æ 定 安 安 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 There is an inevitable connection with gravity, and even pressure is equal to gravity.
In order to make the students clear the pressure and gravity, it is now compared from the following aspects.
Pressure is the force acting perpendicularly on the surface of an object.
Gravity is the force generated by an object being attracted to the earth.
The range of force applied objects with different pressures can be earth, table and chair, wall, person, and can be any object.
There is only one object of gravity, and that is the earth.
(Only near the Earth, not beyond the Earth).
The point of pressure is at the object's 4:.
The point of gravity is at the weight of the object (measured by the "suspension method").
The direction of pressure can be up, down, left, right, and in any direction.
The direction of gravity is only the only vertical down. (But the direction of gravity is consistent. The idea is wrong. For example, the gravity directions of objects in China and the United States are vertically downward, but they may be relative).
There are more pressure and gravity icons, just a few examples.
(3) is a pressure diagram, and figures (4), (5) and (6) are gravity diagrams.
The size is not necessarily the same. Use a pressure of 100 N to press the weight of the 20>' on the vertical wall. At this time, the pressure is 3 cattle, and the gravity of the brick is only 20 cattle. 'An object weighing 100 cows is placed on a slope with a tilt angle of 60*. At this time, the pressure of the object facing the object is N = Gcos6*=100 cattle, and the object whose gravity is still 100 cows*100 cows is placed on the horizontal table and is stationary. At this time, the pressure on the object on the table is Af== 100 cattle, and the gravity of the object is also 100 cattle.
This is the relationship between friction, roughness of the contact surface, and positive pressure. In the case where the roughness of the contact surface is constant, the friction is proportional to the magnitude of the pressure* (the static friction is to be analyzed separately).
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