"Atmospheric Pressure" Pressure PPT courseware 8

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"Atmospheric Pressure" Pressure PPT courseware 8

Import new lesson

Our earth is covered by an atmosphere hundreds of kilometers thick. Most of them are distributed within tens of kilometers above the earth's surface. We live in an "ocean" of atmosphere. This thick layer of gas is often called the atmosphere.

What is atmospheric pressure?

Air is affected by gravity and can flow, so there is pressure inside the air in all directions. The pressure of the atmosphere on objects immersed in it is called atmospheric pressure, or atmospheric pressure or air pressure for short.

1. The existence of atmospheric pressure

Experiment 1: "Cup Covering Experiment"

(1) Place a piece of paper at the bottom of the cup, turn the device upside down and find the cardboard ____

(2) If you fill the cup with water and seal the opening with a piece of paper, and quickly turn the device upside down, you will find _______________.

(3) Pour out the water and cover it with a piece of paper. The piece of paper ________.

(4)What force holds the water and paper ______________.

2. Measurement of atmospheric pressure

(1) Video of estimating the value of atmospheric pressure.

Principle: P=F/S

It can only estimate atmospheric pressure, which is not accurate.

② Turn the glass tube upside down and place it in the mercury bath

③ After the liquid is still, measure the height of the liquid column in the glass tube to about 760 mm.

Analysis: There is a vacuum above the mercury surface in the glass tube, while the mercury surface outside the tube is subject to atmospheric pressure. It is the atmospheric pressure that supports the 760 mm high mercury column in the tube, that is, the atmospheric pressure is equal to the pressure generated by the 760 mm high mercury column.

④ Tilt the glass tube and measure the height of the liquid column in the glass tube to still be 760 mm.

Analysis: The pressure generated by the liquid column in the glass tube is only related to the vertical height of the liquid column and has nothing to do with the thickness, bending, and inclination of the tube. When the tube is tilted, the length of the mercury column increases but its height remains unchanged.

Summary

Cause: Air is affected by gravity and fluid.

Direction: Towards all directions.

Proof of existence: Magdeburg Hemisphere Experiment.

Determination: Torricelli test.

The value of standard atmospheric pressure: 1.01 × 105 Pa.

The law of change: the higher it is from the ground, the smaller the air pressure is.

Class exercises:

1. Which of the following phenomena has nothing to do with the existence of atmospheric pressure ( )

A. Block the small holes in the teapot so that the water in the teapot will not flow out easily.

B. Use a syringe to push the solution into the muscle

C. A piece of paper can hold a glass of water

D. Two pieces of glass are put together and there is water in the middle. It is difficult to separate them.

2. Which of the following examples does not belong to the use of atmospheric pressure ( )

A. Use a centrifugal pump to pump water up from a deep well

B. Pascal burst the barrel with a cup of water

C. In summer we drink through straws

D. Make a small hole in the lid of the teapot

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For more information about the "Pressure, Atmospheric Pressure, Strong" PPT courseware, please click on the Pressure ppt Atmospheric Pressure ppt tag.

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Update Time: 2024-10-01

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