Summary of common physics formulas in junior high school
1, speed: V=S/t
2. Gravity: G=mg
3. density:? = Male/Female
4. pressure: p=F/S
5. liquid pressure: p=? somatotropin
6. Buoyancy:
( 1)F float =F？ -F (differential pressure)
(2)F float =G-F (apparent gravity)
(3)F floating =G (floating, suspended)
(4) Archimedes principle: F float =G row =? Liquid gV discharge
7. Lever balance condition: F 1 L 1=F2 L2.
8. ideal slope: F/G=h/L
9. Ideal pulley: F=G/n
10, actual pulley: F=(G+G movement) /n (vertical direction)
1 1, work: W=FS=Gh (lifting an object very high)
12, power: P=W/t=FV.
13, working principle: w hand =W machine.
14, actual machinery: w total =W plus +W extra.
15, mechanical efficiency:? = Yes/Total
16, pulley block efficiency:
( 1)? =G/ nF (vertical direction)
(2)? =G/(G+G motion) (excluding vertical friction)
(3)? =f/nF (horizontal direction)
thermology
1, endothermic: q endothermic =Cm(t-t0)=Cm? t
2. heat release: Q =Cm(t0-t)=Cm? t
3. calorific value: q=Q/m
4. Efficiency of furnace and heat engine:? =w has /Q fuel.
5. thermal balance equation: Q- discharge = Q- suction.
6. Thermodynamic temperature: t = t+273 K.
electrotherapy
1, current intensity: I=Q power /t
2. Resistance: R=? letter of credit (L/C)
3. ohm's law: I=U/R
4, Joule's law:
( 1)Q=I？ 2Rt general formula)
(2)Q=UIt=Pt=UQ power =U? 2t/R (pure resistance formula)
5, series circuit:
( 1)I=I 1=I2
(2)U=U 1+U2
(3)R=R 1+R2
(4)U 1/U2=R 1/R2 (partial pressure formula)
(5)P 1/P2=R 1/R2
6, parallel circuit:
( 1)I=I 1+I2
(2)U=U 1=U2
(3) 1/R = 1/R 1+ 1/R2[R = R 1r 2/(R 1+R2)]
(4)I 1/I2=R2/R 1 (shunt formula)
(5)P 1/P2=R2/R 1
7. Fixed value resistance:
( 1)I 1/I2 = u 1/U2
(2)P 1/P2=I 12/I22
(3)P 1/P2=U 12/U22
8. Electricity:
(1)W=UIt=Pt=UQ (general formula)
(2)W=I？ 2Rt=U？ 2t/R (pure resistance formula)
9. Electricity:
(1)P=W/t=UI (general formula)
(2)P=I？ 2R=U？ 2/R (pure resistance formula)
10, electromagnetic wave: c=? f
A summary of junior high school physics learning methods and skills
First, rote learning?
Grab it! Basic concepts should be clear, basic laws should be familiar, and basic methods should be skilled. You must be familiar with the text and remember the knowledge points clearly. At least the illustrations in the textbook have a clear impression in your mind, and you don't have to remember how many sides they are, but at least you know what knowledge points it is about, what phenomena it demonstrates, and what it is at last, whether it is on the left page or the right page, so you can expand and understand it.
Second, complete a certain amount of homework independently.
Do some problems independently with good quality and quantity (meaning not relying on others). There must be a certain number of topics, not too few, but also a certain quality, that is to say, there must be some difficulty. Anyone who studies mathematics and physics can't learn this level well. Solving problems independently may sometimes be slow, sometimes you have to take detours, and sometimes you can't even solve them, but these are normal and the only way for any beginner to succeed. It will be very rewarding to hold a meeting on topics that you can't learn and expand your knowledge.
Third, pay attention to physical process and auxiliary drawing.
To be clear about the physical process, whether it is a theoretical process or a practical process, there must be hidden problems in solving problems if the physical process is not clear. No matter how difficult the topic is, try to draw as much as possible, some can draw sketches, and some need to draw accurate pictures, using compasses, triangles, protractors and so on. To represent geometric relationships. Drawing can turn abstract thinking into image thinking and master physical process more accurately. With this diagram, we can make state analysis and dynamic analysis. State analysis is fixed, dead and discontinuous, while dynamic analysis is alive and continuous.
Fourth, pay attention to the lecture in class.
Listen carefully in class and don't be distracted. Don't be self-righteous, learn from teachers and classmates with an open mind. Don't give up listening just because the teacher speaks simply. If this happens, it can be regarded as review and consolidation. Try to be consistent and synchronized with the teacher, and discuss different opinions with the teacher after class. You can't do it yourself, otherwise you will be completely self-taught. After getting started, with a certain foundation, you are allowed to have your own activity space, that is, you are allowed to have something of your own. The more you learn, the more things you have.
Fifth, keep taking notes.
Class is mainly based on listening, and there are notebooks, and some things should be written down. Knowledge structure, good problem-solving methods, good examples, places you don't understand, etc. Should be recorded. After class, you should organize your notes. On the one hand, you should "digest" and on the other hand, you should supplement your notes. Notebook is not only to remember what the teacher said in class, but also to make some reading notes. Good problems found in homework and good solutions should also be recorded in a notebook, which is what students often call a "good problem book". Hard-won notebooks should be numbered, studied later and kept for life.
Sixth, organize the study materials.
Learning materials should be well preserved, classified and marked. The classification of learning materials includes exercises, papers, experimental reports and so on. Correcting refers to, for example, correcting exercises, generally not correcting, and correcting good questions, valuable questions and error-prone questions with different scores, such as *,? , ※, ◎ and so on. For future reading, marking can save a lot of time.
7. Cherish time and improve learning efficiency.
Time is precious. If you don't have time, you won't have time to do anything, so pay attention to make full use of time and improve learning efficiency. Using time is a superb art, for example, we can save time by "recalling" learning methods. Before going to bed, on the way to school, while waiting for the bus, etc. We can recall the lessons of the day section by section, so that we can learn them again and again and achieve the goal of strengthening. Some physical problems are more difficult, and some problems may be solved suddenly while walking. People who study physics often have several problems in their minds that they can't do and won't forget. I don't know when they will make a breakthrough and find the answer to the question.
Eight, "correct attitude, open to the outside world, learn from each other's strengths."
We should learn from others, from our classmates, from people around us and see how others learn. We should often have "academic" exchanges with them, teach each other, learn from each other and improve together. We must never be self-righteous. Cann't be conservative Tell others if you have a good method, so that others will tell you that you have a good method. You should have some good friends in your study. The most taboo is to give up on yourself. "Anyway, I didn't get good grades and couldn't get into a key high school" is suicide and hopeless self-destruction. It will make people lose the motivation to continue.
Nine, pay attention to the systematization of knowledge.
We should attach importance to the knowledge structure, master it systematically, and systematize scattered knowledge. From the whole knowledge structure of physics to the knowledge structure of mechanics, even to chapters, such as the knowledge structure of statics and so on. This flexible way of thinking will confuse the whole physical knowledge and make people think more easily.
Ten, pay attention to the number of words and "minor courses" to understand the importance of complementarity between disciplines.
The calculation of physics depends on mathematics, which is too important for learning physics. Physics is difficult to do without mathematics as a calculation tool. After arriving at the university, the math class in the physics department is as important as the physics class. We must learn math well and make good use of this powerful tool. We should also make good use of Chinese as a tool, which can help us understand the physical meaning more accurately. If you can learn biology, geography and other "minor courses" that students think are good, it will also play a very important role in learning physics. Because all classes do not exist independently, but are interrelated. And comprehensive topics are very popular now.
Pay attention to the development and training of thinking in learning.
Some students also want to learn, and they are really studying hard. These teachers can see that, but their grades are still not ideal. On the other hand, students are careful in class, neat in homework and meticulous in notes, but they don't know what to do from another angle and method. Most of these students are not completely stupid, mainly because of thinking problems. Common thinking disorders are as follows:
1, thinking obstacle formed by preconceived life concept.
2. Obstacles caused by confusion of similar physical concepts.
3. Thinking disorder caused by improper analogy.
4. Thinking obstacles formed by mathematicization of physical formulas.
5. Thinking obstacles formed by vague concept connotation and extension.