Finally, chaotic physics, a physics problem that left me confused

Assuming that the propagation speed of this sound is 1000 seconds, then it takes 1000 seconds to propagate 1 km.

12 seconds 3 seconds = 4 times the distance between the ridge and the reed ridge is about 4 1km = 4km

The learning of physics is modular and is divided into four modules: 1 The understanding of concepts cannot be simply memorized. When faced with a new physical quantity, it is important to understand its role in the actual problem solving.

2 Application of the concept: Once the concept is understood, there is no major problem in applying it. The solution to the problem is, to grasp, every sentence in each question is giving you conditions, as long as the conditions correspond to the physical quantities, and then substitute into the corresponding formula, you can solve the answer.

3 Derivation 4 Synthesis: In the various chapters of physics, except for the relative independence of optics, the others are closely related, and care must be taken to connect them with each other. 2. How to do the exercises:

When doing exercises, especially science exercises, it is necessary to grasp the relationship between quantity and quality. Mainly focus on the quality of the questions. "I" never bought exercises in high school, mainly after completing the questions in the book and the questions given by the teacher, I summarized the solution ideas for each problem.

The process of solving the problem is divided into: 1 Analyzing the physical process: abstracting the process into physical quantities 2 Using mathematics to solve the problem 3. Study habits

1) You should listen carefully in class, and as for the learning method, you should adapt the learning method to yourself, rather than allowing yourself to adapt to the methods that others use well. 2) Think more and ask more questions when doing questions. "I" have always been very slow to do the questions, but every time I finish the questions, I look at how I got them, see what I can learn from in the future, and achieve the effect of drawing inferences from one another, instead of leaving them behind after I finish them.

In this way, "I" will be fast when I take the exam, unlike others, and when it comes to the exam, I will be busy deducing. 3) Ask questions immediately when you make mistakes, discuss problems with teachers and classmates, and don't be shy. 4) Review over and over again.

5) For reference books, students who do not have very good grades should look for books that have better analysis and summary when buying, rather than books that simply give answers. Satisfied.

1.Cathode.

Generally speaking. The power source below also serves the purpose of providing an electric field for electrons. Electrons come out from the right. It is accelerated to the left by an electric field. So there is an electric current.

2.Electron. 3.Misspelled =.=...

ps.The mouse in someone's space is actually it. $ drooling....

You are right in the first question, for the second question of the density of hydrogen, I will teach you, the density is equal to the mass divided by the volume, and then you think, in a sealed bottle, the mass becomes smaller, and then the volume of the bottle does not change, then it means that the density of hydrogen has decreased, can you understand this?

Question 1: This question is a question of overweight and weightlessness, and if you figure these two out, the question will be clear. weightlessness, the pressure is less than its own gravity; Overweight, the pressure is greater than your own gravity!

So if you imagine the condition of the goods, you will know the answer, and the answer is point A B.

Question 2: This question is to examine the conservation of your energy. The kinetic energy of the bullet = the common kinetic energy of the bullet and A, and the velocity of A when the bullet just passes through A.

Examine the conservation of momentum: You think of bullets, a, and b as a system, which is not subject to external forces, so it is suitable for conservation of momentum.

The equation goes like this, the initial momentum of the bullet = the final momentum of the bullet + the momentum of the AB system.

In this way, the velocity of ab as a whole at relative rest is solved.

Then, according to the initial velocity of A solved in the first question, plus the final velocity of A now solved (i.e., the common velocity of burning and letting AB get the same velocity), A does a uniform deceleration motion on B, and the required distance can be found in the code!

1 A and B2

If you don't understand, you can contact me.

The volume and density are proportional when the mass is constant. Hydrogen is a gas that can diffuse in a hydrogen cylinder, i.e. the volume remains the same. At this time, the mass of hydrogen is proportional to the density, so it decreases.

The mass of the hydrogen cylinder decreases and the volume remains unchanged.

Forced.

Because according to Newton's first law: all objects will remain in a state of uniform linear motion or a state of rest when they are not subjected to force.

The spaceship in this problem is neither stationary nor moving in a uniform straight line, but in a circular (directional) motion, so it must be subjected to force.

The reason why space is said to be weightless is because the centripetal force is just used to maintain the circular motion, the centripetal force of the person is used to maintain the circular motion of the person, and the centripetal force of the spacecraft is used to maintain the circular motion of the spacecraft. In high school, you will learn this formula: f=gmm (r squared) gravitational formula, and centripetal force formula f=m(v squared) r, then there is gmm (r squared) = m (v squared) r, and v = mg r under the root number, which is a fixed value, and the speed of people and spaceships is the same, relatively stationary, and it feels like people are floating in spaceships.

The force it is subjected to is exactly equal to the earth's gravitational force and centrifugal force, so it is a weightless state.

Weightlessness is a state, not the absence of weight or gravitational force.

The force is subjected to the gravitational pull of the earth as a centripetal force in a circular motion.

It's like if you throw something, when it falls in an arc equal to the arc of the earth, it never falls to the ground.

It is affected by the fact that it moves in a curve and is weightless, and it is also forced, but it is not counted.

Of course, the force is forced, and the gravitational force is used as a centripetal force, so it can do circular motion.

The weightlessness of the people in the spaceship is due to the fact that gravity acts as a centripetal force to overcome the tendency of people to fly outward.