Can anyone write out the thinking of physical atmospheric pressure in the second year of junior high

Atmospheric pressure is caused by the fact that air has weight; Air is fluid.

Experiments to prove the existence of atmospheric pressure: Alto Glick's Madberau Hemisphere Experiment.

Experiments for measuring atmospheric pressure values: Torricelli experiments.

The value of a standard atmosphere: 1atm = 76 cmHg =

There are two common barometers: U-tube barometer and metal box barometer. The metal box barometer can be converted into an altimeter.

The value of barometric pressure is related to the season and weather. Winter and sunny weather are high; Summer and cloudy weather are depressed.

The boiling point of a liquid is related to the air pressure above the surface of the liquid. The higher the air pressure, the higher the boiling point of the liquid. This is how a pressure cooker works.

The relationship between flow velocity and pressure: the higher the flow velocity, the lower the air pressure; The lower the flow velocity, the greater the pressure. This is how the lift of an aircraft is formed.

Gas does not have a definite shape, it always fills the space that can be reached, and its shape is the same as that of a container.

Does it mean that atmospheric pressure is generated? Because air has mass, and it is believed that it is evenly distributed everywhere, under the action of the earth's gravitational force, there will be pressure per unit area, which will produce pressure, and gas and liquid can both transmit pressure, so if the height is the same, the pressure everywhere is equal, to put it bluntly, it is a truth to feel the pressure of water in water, but this water is replaced by air.

Actually, this is very understandable

1.The reason why the drink sealed in the bottle cannot be sucked out is because the atmospheric pressure outside the bottle is much greater than the atmospheric pressure inside the bottle, so the drink inside the bottle is squeezed by the atmospheric pressure outside, so the drink in the bottle cannot be sucked out.

2.In the Magdeburg hemispheric experiment, because the inside of the sphere is vacuum, the two hollow copper balls are tightly pressed together by the atmosphere. Thus, this experiment proves the existence of the force (atmospheric pressure) that holds the two balls tightly together, and the existence of atmospheric pressure.

As for Torricelli's experiment, the value of atmospheric pressure was measured for the first time by the height of the mercury pressed by atmospheric pressure (the specific steps are explained in detail in the book, if you don't understand, you can take a good look at lz).

The standard atmospheric pressure to the fifth power of the Pa represents the force to be experienced by the fifth-power Newtons from the atmosphere per square meter in the local area.

Hope it helps

lz must adopt the original mobile phone party is not easy).

The essence of drinking a drink is to suck the air out of the straw, and the pressure in the straw is less than the atmospheric pressure, and the atmospheric pressure will press the drink out of the bottle.

First of all, the Magdeburg hemisphere experiment is to pump the two hemispheres into a vacuum, so that the air pressure inside and outside the ball is unbalanced, and the outside atmospheric pressure compresses the two hemispheres tightly together, so it is difficult to separate the two hemispheres, so the existence of atmospheric pressure can be proved.

In the Torricelli experiment, the mercury column is inverted in the mercury tank, so the test tube is sealed, and the mercury column in the test tube will not fall, because of the presence of atmospheric pressure, the mercury column is propped up. The Torricelli experiment measured that the standard atmospheric pressure is the fifth power Pa, which can be expressed as 760mmHg, that is, from the formula p=f s, we can get p = kilogram cubic meter (density of mercury) Newton kilogram meter Newton square meter = Pascal.

Because the lower surface of the square iron block and the upper surface of the table are not completely smooth and cannot be completely touched together, the lower surface of the iron block still has atmospheric pressure, so it is only a balance of gravity and support. If, in a very ideal state, the lower surface of the square piece of iron and the upper surface of the table are very smooth (they can be perfectly attached), then the atmospheric pressure to which it is subjected will not be offset and it will be difficult to pick up. However, the general title will not give such a very ideal situation, so there is no need to consider this situation if it cannot be pasted together on the surface without special instructions.

(1) The length of the full scale of the syringe l, and the indication f of the spring dynamometer when the syringe piston just starts to slide

2) The atmospheric pressure at the summit of the mountain p=fl v

3) The height of Huaguo Mountain h=10(P0V-FL) δPV

The atmospheric pressure is much greater than the sum of the pressure of water on the test tube, so the test tube does not fall down, but rises.

It is to choose C, there is no gas on the top of the small test tube, there is no air pressure, and there is atmospheric pressure below, and the small test tube is pressed up.

There is no diagram case'Estimate option A

There's no picture.,Send it up.。

c. The water stops flowing after a little flow into the plastic cup.

The inside of the cup begins to flow in with gravity as the water flows in the same atmospheric pressure. But slowly the volume of the bottle becomes smaller, the pressure in the cup will become larger, greater than the outside atmospheric pressure, when the atmospheric pressure in the cup = gravity + outside atmospheric pressure when the water can not enter.

c, the water begins to enter, and the pressure in the cup slowly increases, and the water cannot flow in.

ml (this number is what you want to measure in the diagram, if you measure it differently, according to yours) s 20cm

2) s p=f s= change this =

3), the partial section of the annihilation is small. On the large side.

The figure is invisible. Empty the syringe with air and close the mouth. The maximum value is measured by pulling the syringe piston through the dynamometer (the syringe is a vacuum, and the friction force is negligible, which is the pressure of atmospheric pressure acting on the piston); The diameter of the piston is measured with a scale and the cross-sectional area s of the piston is calculated, and the solution is solved by using p=f s.

3) Small: Small.

Hello, I didn't see your picture.

2) The experimental procedure is as follows: repeatedly pull and pull the air in the syringe to drain it, plug the mouth with your fingers or other things, and then pull the syringe piston with a dynamometer, and when it is pulled out, write down the value and write down the value of the force acting on the atmospheric pressure. Since the syringe is approximately vacuum, and the friction is negligible, the dynamometer measures the pressure of atmospheric pressure acting on the piston; Finally, after measuring the diameter of the piston, the cross-sectional area of the piston s=pi * r 2 is calculated, and then the atmospheric pressure is solved by the formula p=f s.

The general results are close.

3) Both are on the small side.

Hope, thank you.

As shown in the picture, fill a small bottle with some colored water, then take a thin glass tube with two ends open, draw a scale on it, make the glass tube through the rubber plug into the water, and blow a small amount of gas from the upper end of the tube to make a simple barometer. Xiao Ming brought the barometer from the foot of the mountain to the level ground at the top of the mountain, and the height of the water column in the glass tube [increased], at this time, due to the maximum height, the outside atmospheric pressure was less than the closed air pressure in the bottle!

The pressure of the water on the bottom of the container [increases]. —p= gh - the maximum pressure of the bottle on the ground [unchanged] - the overall total mass does not change - the gravity does not change - the pressure does not change - the bottom area does not change - the pressure on the ground does not change!

The barometer is brought from the foot of the mountain to the level ground at the top of the mountain, and the height of the water column in the glass tube becomes larger, and the height increases, and the outside atmospheric pressure becomes smaller, so the external atmospheric pressure is less than the closed atmospheric pressure (atmospheric pressure) in the bottle!

The pressure of the water on the bottom of the container [increases]. —p= gh - h becomes larger, and the pressure on the bottom of the container increases.

The pressure of the bottle on the ground [unchanged] - the overall total mass does not change - the gravity does not change - the pressure does not change - the bottom area does not change - the pressure on the ground does not change.

You're talking about experimenting with water, not mercury.

In the Torricelli experiment, if a small hole is made in the top of the tube, the tube becomes a glass tube with openings at both ends.

In this case, the height of the water surface inside the pipe is about the same as the height of the water surface outside the pipe.

If the inner diameter of the pipe is smaller, the water surface height inside the pipe may be slightly higher than the water surface outside the pipe due to capillary phenomenon.

There will be no upward flow of water.

Hello subject, you are thinking very right, if there is a vacuum above the nozzle, your answer must be right. But the fact is: when a small opening is made at the top, the mercury in the pipe will appear on the top and the air directly, and the pressure of the mercury on the top of the mercury is as large as the pressure of the mercury in the tank, so that the mercury falls into the tank due to gravity.

What you said about the high pressure due to the large area is not true. It mainly depends on the pressure per unit area, that is, the pressure.