For junior high school welfare learning, at least in the senior high school entrance examination, there will be no too difficult questions.

First of all, we should pay attention to several points when doing the topic of buoyancy.

1, first determine the state of the object: floating, floating and sinking.

2. Determine which part of the object is floated. For example, a T-shaped object that sinks to the bottom does not float upside down, but only the feet on both sides float.

3. Determine the density, volume, mass and height of the object, and calculate the buoyancy in some specific topics. The buoyancy can be calculated by the difference between the upper and lower sides of the object under the pressure of water. Of course, the senior high school entrance examination will not appear, because this topic is already difficult.

4. It should also be noted that it is used in density, Archimedes theorem and other formulas. Sometimes you don't need to deduce all of them, but you can solve them directly by algebraic method, which requires you to skillfully use various formulas and deformations related to density, volume, mass and Archimedes theorem.

5. It is necessary to pay attention to the changes in the mass and volume of objects in some operation problems. For example, a balloon suspended in water, I added a little water to it and asked how the state of the balloon changed.

6. Also analyze the forces. If the analysis is correct, the balance force is suspended (there is no supporting force in these forces), and the unbalanced force, where the force is large, the object moves in the opposite direction.

7. Finally, the buoyancy is calculated, and the calculation is needless to say. The most important and easily overlooked thing is the conversion and unification of units, and the calculation should also pay attention to methods, which is closely related to mathematics. Of course, physics only pays attention to methods here, and does not discuss how mathematics is converted.

Regarding the topic of close contact mentioned above, I would like to explain here that as long as there is no precise contact between the objects in the topic, it will default to close contact, otherwise it will be stated in the topic that there is no precise contact between the objects, or it can be clearly implied in the topic and calculation that there is no precise contact affecting the calculation results. At this time, it is necessary to consider that there is no precise contact.

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