Ask a simple junior high school physics question, a simple junior high school physics question.

In two cases, the increase is obvious on the main road, and the increase on a certain branch road will also increase the resistance of this part, as in the example of 1 ohm and 100 ohms: the original resistance is 100 101 ohms, if it increases by 1 ohm, then it will be closer to the increase (he to a few ohms), this is the trend, if it increases by 100 ohms, then it also increases, this is less obvious than the former, the amplitude is not very high, you can use the mathematical formula to push down r=r1r2 (r1+r2), so that it is clearer.

Definitely. Take two resistors in parallel as an example:

r and r1*r2 (r1+r2).

r1/（r1/r2+1）

Suppose r2 increases.

r and will increase.

It must not be increased;

Because in a parallel circuit: 1 r = 1 r + 1 r, where r represents the total resistance, and r represents one of the remaining resistances.

From the above formula, it can be seen that the total resistance must be reduced from the parallel connection of a resistor.

Enlarge by all means. rTotal 1 1 r1 +1 r2 +r3

So when r1 increases, 1 r1+1 r2 decreases.

1 1 r1 + 1 r2 +r3 increases.

In the parallel circuit, 1 r + 1 r = 1 r total, so the resistance value of one resistor in the parallel circuit increases, and the resistance value of the whole parallel circuit must increase.

Not necessarily. Two resistors in parallel The total resistance should be closer to the small one. So if one is 1 ohm and the other is 1,000,000 ohms, the total resistance is close to 1 ohm.

Not necessarily. Collusion and reversal, this is fine.

The first one is force decomposition.

When the car winds up the mountain, the slope of the uphill road is smaller than the slope of the mountain, which is equivalent to climbing a steep slope before, but now the slope is flat, of course, it requires a small traction to go up the mountain.

Yes. Let the original slope of the hillside x0, and now the slope of the winding road x1, there must be x1, and the second is the conservation of energy.

The power p that the tractor can provide to the outside is certain, that is, the work w that can be done externally per unit time is certain.

By w=f*s, both sides are divided by time at the same time, i.e. w t=f*s tw t due to =p, s t=v

Therefore p=f*v

That is, the product of traction and speed is colonization, so slowing down the speed increases traction.

1.The density and temperature inside and outside are the same at first, but just cover a lid, of course, it does not affect the pressure inside. The change in atmospheric pressure varies very little with altitude, and the height of the bottle is negligible.

2.If you haven't learned, you can analyze the cause of air pressure, the density of the air in the bottle increases, and the number of gas molecules per unit volume increases, so the more molecules per unit time and the bottle per unit area avoid colliding, the greater the pressure.

Because before sealing, the air pressure inside the bottle is equal to the atmospheric pressure, and even if it is sealed, it is still the same. Because the bottle is placed in the atmosphere before sealing, and the air flow is uniform, don't think too much about it. When you blow air into the bottle, the density of the gas in the bottle increases, and the pressure per unit surface area in the bottle increases, so the pressure increases, and the air pressure in the bottle is equal to the atmospheric pressure.

Don't ask anymore why it's equal because it's in the air.

You understand that there is a misunderstanding, when the bottle is not capped, the internal and external atmosphere is connected, and there is no objection to the equal pressure inside and outside the bottle, and after the lid is closed, it does not mean that the air column above the lid does not exist, and the air column above the lid can also transmit the pressure to the gas in the bottle through the lid, so with or without a lid, for the gas in the bottle, the air pressure will not change. To understand with your air column, without a lid, the height of the air column is the height h from the bottom of the bottle to the top of the atmosphere, and after adding the lid, the height of the air column is the height of the bottle h1 + the height of the lid to the top of the atmosphere h2, regardless of the thickness of the lid, h1 + h2 = h. Therefore, the pressure inside the bottle is the same as the pressure outside.

In the same way, if you hold a bottle full of water and put it in water, the water pressure inside the bottle with or without a lid is the same as the water pressure outside the bottle, regardless of the depth of the bottle.

I don't know if you mean the height by depth. If so, it's understandable:

1 Air pressure is caused by the thermal motion of the molecules striking on a flat surface. The magnitude of the air pressure is related to the number of impacts (per unit time) and the velocity of the molecule, which is mainly related to the concentration of the molecule and the temperature.

When the glass bottle is sealed, there is a heat exchange with the outside world. The temperature is the same. The molecular concentration varies in the strict sense, because the density of the air in the glass bottle does not change, while the density of the atmosphere is different, the upper layer is thin and the bottom layer is dense.

So h doesn't change much. It can be considered that the internal and external air pressure is the same.

2. As the density increases, the molecules that collide on the plane (the surface of the glass bottle) between units increases, and the pressure increases.

In fact, the pressure of the gas inside the container is determined by the temperature and density of the gas. The gas molecules are in a never-ending thermal motion, frequently hitting the walls of the device, generating pressure. The greater the number of molecules impacted per unit area and the more intense the impact, the greater the pressure generated.

And the higher the temperature, the higher the density, and the greater the pressure. If the gas inside the container is the same density and the same temperature as the atmosphere, then the pressure generated will be the same. If the density or temperature is higher than the outside air, then the pressure will be greater than the outside air.

I don't know if you can understand this, but this is what you learned in high school physics.

: Atmospheric depth refers to the distance from the ground, the closer to the ground, the greater the atmospheric pressure, the farther away from the ground, the smaller the atmospheric pressure, and the bottle is also on the ground, it is the same atmospheric depth, so the atmospheric pressure is equal.

Blowing air into the bottle, the density increases, but the volume does not increase, and the amount of gaseous substances per unit volume does not change, so the pressure does not change! (The quantity of matter is a concept learned in high school, which refers to the number of molecules).

The air pressure is not only to the bottom, but to all directions, and the atmospheric pressure increases with the increase of the depth of the atmosphere, which refers to the same layer.

1Because the air pressure in the bottle does not change, does the book say that the air pressure increases with the altitude? 2. There is a problem with the question you asked. Note, I'm always angry with you.

It's not all about the increase in density, it's about the increase in internal energy.

Personally, I think d, because the metal ball will float in B.

This knowledge is the application of the connector. The communicator is the content of the third year of physics.

There is no need to mark the tube.

Communicator Principle:

When the water in the tube is still, mark the position of the horizontal plane in the tube on the wall.

You can assume that there is a small liquid sheet at the bottom of the pipe, when the water level at both ends of the pipe is different, the pressure on the left and right sides of the small liquid sheet is different, and the pressure on the higher side of the water level is strong, and the pressure of the water is greater, so that the small liquid sheet moves to the other side until the water level on both sides is equal. (At this point, you are assuming that the pressure on both sides of the small piece of liquid at the bottom of the tube is equal, then the pressure wants to wait, and it is not moving.) The water in the entire tube no longer moves.

That is, the water surface at both ends is on the same level.

Are you satisfied?

It's just the principle of the connector, can't you change the knowledge without learning, right? Other applications include teapots, boiler water level gauges, ship locks, and more.

If you're using the human education version, the connector is the content of the third year of junior high school, so there's no need to ask if you haven't learned it yet.

Isn't it the principle of atmospheric pressure? It's the atmospheric pressure that makes the water surface on both sides the same height.

In junior high school, there was a principle of connectors, at least I learned.

The clear plastic tube is scaled, it's not filled with water, there's a little bubble, and when the bubble is at 0 on the scale, the plastic tube is horizontal, and the physics used is that the air is dense, the water is dense, and the air is always on top of the water.

How do you explain it without a connector?

Try to explain to you that the left and right ends of the plastic pipe are subject to atmospheric pressure, and the radius of the plastic pipe can be seen as equal everywhere, so the atmospheric pressure at both ends is equal, so the horizontal plane at both ends is equal.

If you look closely, you'll see that there's a little bubble in that transparent tube, and when the tube is level, the little bubble is in the middle of the tube, and this instrument is often used in physics experiments, called spirit levels.

Since there is no communicator principle, it is Newton's first law. It is the "object acting on the balancing force moving in a straight line or at rest at a uniform speed". When the water is on the same horizontal line, any drop of water in the water pipe will be balanced and will not move.

Pushing back, the water does not move, indicating that the water droplets are under equilibrium, indicating that the water is on the same level.

。If the same liquid is contained in a U-shaped glass tube, imagine a small liquid sheet AB in the middle of the bottom of the communicator. Suppose the liquid is still and does not flow.

The pressure of the liquid in the left tube to the right of the liquid sheet ab must be equal to the pressure of the liquid in the right tube to the left side of the liquid sheet ab. Because the communicator is filled with the same liquid, and the density of the left and right liquid columns is the same, according to the formula of liquid pressure P= Gh, it can be seen that the pressure of the liquid columns on both sides can be equal only when the height of the liquid columns on both sides is equal. Therefore, in the case that the liquid does not flow, the liquid level in each container of the communicator should be kept flat.

It is indeed the communicator principle. It looks like I've already learned in junior high school, right? The application in life is the kettle, and without the principle of the communicator, there is no way for the water to be poured out of the spout.

It's really the principle of a communicator, which you definitely have to learn in junior high school, and you should learn it in the third year of junior high school.