I didn t learn physics well in the second semester of junior high school, and we are about to take t

If you can't memorize it, then understand the memory, first of all, you have to understand what you remember, such as what a letter represents, and then you have to remember the formula, under the condition of knowing the meaning of the letter, go down to ask the teacher how to get the formula, but the teacher may use the previous formula to deduce the answer, so you have to start over, it may be more embarrassing, you can also read the book by yourself, but it is a little difficult, anyway, after understanding how the formula came about, the postscript is not a boring letter, It's a process of pushing, and after remembering the formula, you have to do the topic to deepen your memory, and if you do more, you will naturally remember it.

As for how to do the problem, you have to analyze it yourself, first of all, you must know what the problem is looking for, and what formulas you know in the formula can be found, and what are the quantities needed to use this formula, and these quantities may not be in the problem, so these quantities also need to be calculated by formulas, and you must find formulas, find the quantities given by those questions that can be used and the results you need to calculate.

Physics is a subject that is learned by understanding and sexual interest. I think there are a lot of questions to do well in physics. If you do too many questions, you will naturally memorize those formulas.

As long as the surface isn't absolutely smooth, you're right.

However, friction is not necessarily a force that hinders relative motion, it can also be a driving force. For example, if a wooden block is placed on top of a book and the book is suddenly moved in a certain direction, we will find that the wooden block also moves in the same direction. At this time, the movement of the wooden block is achieved by friction.

First of all, the condition for the existence of friction is that there is a tendency of relative motion between two objects, which may be in motion with each other or at rest with each other, and the two planes are required to be rough. A flat surface is absolutely smooth and does not produce friction. There are many theories that the cause of friction is that the surface of the object is not smooth, resulting in the uneven parts of the object filling each other and not moving, and some believe that it is the interaction force of molecules on the surface of the object.

The most important physics in the second year of junior high school is Ohm's law and the electrical power part. I don't know if you talked about it or not, but if you do, you must review it. Then it is to keep a good record of the voltage and current law of the series circuit and the law of parallel voltage and current, I dare to say that these two contents must be examined, but I dare not say that I dare to test the series and parallel, and the experimental principle of measuring the small bulb and the fixed value resistance with voltammetry

From Ohm's law r=u i, "from Ohm's law" must be written, otherwise no points will be given. What I said is the most important, must know the content, and then the rest is a small knowledge point, you just look at the notes, memorize well, and then put the formula of electric power, Ohm's law part of some typical questions, I think it's no problem, there are 5 days, use my method to review, 5 days everywhere, as long as you study hard, you can learn a lot in 5 days.

We take the physics test the day after tomorrow, and it is also the second year of the people's education version, Ohm's law, electric power, current characteristics, resistance and current, voltage, electric power, the ratio of electrical work must be examined, the calculation questions should be carefully examined, understand the change circuit, and find the 5 formulas of electric power p=iu=i r=u r=w t=(u real u amount) *p amount, 4 formulas for finding electric work: w=pt=i rt=uit=u r, you just need to remember these formulas, and the characteristics of series and parallel current and voltage.

The midterm exam is generally not very difficult, tell me your email address, and I will send you a test question to do.

Find a review material for the high school entrance examination, such as the total review of the high school entrance examination in the gold list case, and spend two or three days reading the scope involved in the midterm exam.

Take memorization notes, especially formulas.

The three blocks have the same volume and the same displacement, so the buoyancy is the same.

And their gravity is different (because of the different densities), so when the gravity is less (less buoyancy) the block floats, when the gravity is greater (when it is greater than buoyancy) the block sinks, and when the gravity is equal to the buoyancy, the block is suspended.

According to the formula f buoyancy = density of the liquid multiplied by g multiplied by v row. The three objects v are equal, so the buoyancy is equal. As for gravity, gravity is determined by the object itself, i.e., the volume multiplied by the density, independent of buoyancy. Light objects float up, heavy objects sink.

Because buoyancy is only related to the mass of the object.

Since the independent variable of ** is the deformation variable, the deformation should be changed every time in the comparative test, and the rubber band with different lengths is only unequal in length, and it is not suitable for the deformation variable.

Here is a difference between rubber band length and deformation, which are different concepts.

What about the picture in your question?