"Atmospheric Pressure" Pressure and Buoyancy PPT Courseware

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"Atmospheric Pressure" Pressure and Buoyancy PPT Courseware

Guess: Is there pressure in the atmosphere?

Analysis: There is pressure in all directions inside the liquid because the liquid is affected by gravity and has fluidity. The atmosphere is affected by ______ like a liquid and has ______ properties. It can be inferred that the atmosphere will also be like a liquid and have ______. And there is pressure in all directions.

Magdeburg Hemisphere Experiment

In 1654, Otto Glick, the mayor of Magdeburg, Germany, conducted the famous Magdeburg hemisphere experiment.

What did the Magdeburg Hemisphere Experiment show?

The Magdeburg Hemisphere Experiment proves that the existence of atmospheric pressure also proves that the atmospheric pressure is very strong.

1. The pressure of the atmosphere on objects immersed in it is called atmospheric pressure. Referred to as atmospheric pressure or air pressure.

There is pressure in the air in all directions

2. Determination of atmospheric pressure: -----Torricelli experiment

(1) Will the results be affected if the glass tube is tilted?

(2) Will changing to a thicker or thinner glass tube affect the results?

(3) If some air leaks in, will it affect the results?

(4) If the outside atmospheric pressure changes, does the height of the mercury column change?

(5) When mercury is added to the tank, does the height of the mercury column change? Why?

Please note the following issues regarding Torricelli’s experiment:

1. This experiment was conducted near sea level.

2. During the experiment, the thickness of the tube, its inclination, lifting it up and pressing it down will not affect the measurement results as long as the mouth of the tube does not leave the mercury surface in the tank.

3. Air leaking into the tube will cause the measurement result to be _____.

4. Open a hole at the upper end of the tube, and let the mercury fall to the level of the mercury surface in the tank.

5. Remember the value of standard atmospheric pressure

P gas =P mercury

=ρmercurygh

=13.6×103kg/m3×9.8N/kg×0.76m

=1.012928×105Pa

The value of standard atmospheric pressure:

It is equal to the pressure generated by a 760mm high mercury column, about 1.013×105Pa. A rough calculation can be taken as 105Pa

3. Atmospheric pressure changes

1. Atmospheric pressure changes with altitude. The higher the altitude, the smaller the atmospheric pressure.

2. Atmospheric pressure is also related to climate

4. Measurement of atmospheric pressure

The instrument that measures atmospheric pressure is called a barometer. There are two types: aneroid barometer and mercury barometer.

The relationship between boiling point and air pressure

in conclusion:

The lower the air pressure, the lower the boiling point.

The greater the pressure, the higher the boiling point.

1. Atmospheric pressure

The pressure inside the air in all directions is called atmospheric pressure.

2. Causes of atmospheric pressure:

Because the atmosphere is affected by gravity, it is also fluid.

3. Magdeburg Hemisphere Experiment:

It proves the existence of atmospheric pressure and also shows that the atmospheric pressure is very large.

4. Torricelli experiment:

First, the value of atmospheric pressure was measured.

P = 760mmHg = 1.013×105Pa

5. Changes in atmospheric pressure:

Atmospheric pressure decreases with height and increases with volume.

6. Application: piston water pump, centrifugal water pump

Test questions

1.__________ Experiment proves the existence of atmospheric pressure. The ____________ experiment measured the value of atmospheric pressure.

2. When the fountain pen absorbs ink, press the spring leaf on the pen a few times. The pressure of the gas in the pen bladder will be ________. Under the action of _________, the ink will be "sucked" into the rubber tube.

3. When doing Torricelli's experiment, if the glass tube is tilted, the mercury column in the tube will ( )

A. The length decreases B. The height remains the same

C. Increase in height D. Decrease in height

4. Which of the following statements is correct ( )

A. The vertical downward pressure of the atmosphere on objects immersed in it is called atmospheric pressure

B. The thicker the glass tube used in Torricelli's experiment, the smaller the height difference between the mercury surfaces inside and outside the tube.

C. Under standard air pressure, the Torricelli experiment can also be performed with an 80cm long glass tube.

D. The tilt of the glass tube will affect the measurement results of Torricelli's experiment.

5. In winter, the thermos bottle is not filled with water, and the cork is not easy to pull out when the temperature inside the bottle drops. This is mainly because ( )

A. The friction between the stopper and the bottle mouth is too large

B. The mouth of the bottle shrinks when exposed to cold

C. The air pressure inside the bottle is less than atmospheric pressure

D. The original plug was too tight

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Update Time: 2024-09-30

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