"Studying the Pressure of Liquids" Magical Pressure PPT Courseware

"Studying the Pressure of Liquids" Magical Pressure PPT Courseware

teaching objectives

1. Know the causes of liquid pressure

2. Know the characteristics of liquid pressure

3. Be able to use the liquid pressure formula to calculate liquid pressure.

4. Know what a connector is and what its characteristics are.

Detection target one

1. Use examples to illustrate whether liquids can generate pressure?

2. What are the characteristics of the internal pressure of liquid?

1. Surprising Experiments

1. Does the liquid exert pressure on the bottom and side walls of the container?

Thinking: What causes liquid pressure?

Since the liquid is affected by gravity, the liquid exerts pressure on the bottom of the container.

Because liquids are fluid, they exert pressure on the side walls of the container that prevent them from spreading.

Is there pressure inside the liquid? What are the rules for pressure inside liquids? How to measure the pressure inside a liquid?

2. An instrument for measuring the internal pressure of a liquid - micro-pressure gauge

The working principle of the pressure gauge: When the rubber membrane on the probe is subjected to pressure, a height difference appears in the liquid level on both sides of the U-shaped tube. The height difference on both sides represents the pressure. The greater the pressure, the greater the height difference in the liquid level.

A pressure gauge is an instrument specially designed to measure the pressure of liquids.

Principle: When the rubber membrane on the probe is subjected to pressure, a height difference appears in the liquid level on both sides of the U-shaped tube. The height difference on both sides indicates the liquid pressure. The greater the pressure, the greater the liquid level difference, and vice versa.

Scientific Method: Transformation Method

Convert a physical quantity that cannot be directly measured or is difficult to measure into a directly measurable physical quantity.

The pressure gauge converts the liquid pressure into the height difference between the liquid levels on both sides of the U-shaped tube. The physical quantity of liquid level difference is used to intuitively reflect the size of liquid pressure, thereby exploring the characteristics of liquid pressure.

3. Analyze and calculate the pressure inside the liquid

Liquid column volume v=sh

Liquid column mass m=ρv=ρsh

Liquid column weight G=mg=ρgsh

The pressure of the liquid column on its bottom surface F=G=mg=ρgsh

The pressure of the liquid on its bottom surface P=F/s=ρgsh/s=ρgh

Calculation formula of liquid internal pressure: P=ρgh

P: internal pressure of liquid

ρ: liquid density

g：10N/Kg

h: depth

Deformation formula: Scope of use: Used to calculate liquid pressure

Use the formula p=ρ liquid gh to perform simple calculations

1. There is a plastic bottle. Use an awl to poke three holes in the side wall. After pouring water into the container, the water spurts out from the small holes. As shown in the picture, the correct one is ( )

2. Compare the relationship between the pressure P of water on the bottom of the three containers with equal bottom areas below.

3. A diver wearing a diving suit dives to a depth of 20m underwater. What is the pressure generated by the water there? (g=10N/kg)

Example: If a student imitates Pascal and does an experiment on a 5-meter-high balcony, what is the pressure on the bottom of the barrel after the thin tube is filled with water? (g is taken as 10N/Kg)

Solution: P=ρgh

=1.0×10³Kg/m³×10N/Kg×5m

=5×104Pa

Answer: The pressure at the bottom of the barrel is 5×10 4 Pa

5. Connector

1. A container with an open upper end and a connected bottom is called a connector in physics.

2. Principle of connector

For the same liquid stationary in the connector, the liquid levels in each container will always remain equal.

3. The connector in life

Operation

After-class exercises: 2.3.4

Preview

1. Give an example to illustrate the existence of pressure in the atmosphere

2. How to measure atmospheric pressure? What is the value of a standard atmospheric pressure?

Give an example of the impact of atmospheric pressure on weather

Give an example of the effect of atmospheric pressure on the human body

summary

1. The liquid has pressure on the _____ of the container because it also has pressure on the ____ of the container, because there is also pressure on _______. We can measure the pressure inside a liquid using _____.

2. The pressure inside the liquid is __________; the pressure inside the liquid increases ______ with the depth; in ______, the pressure of the liquid is equal in all directions.

The pressure of a liquid is also related to the density of the liquid. When the depth is the same, the greater the density of the liquid, the pressure _____.

3. The connector is a container with _________ on the top and _________ on the bottom. Only when ________ liquid is injected into the connector, and when the liquid _______, will the liquid levels in each container remain level.

Class exercises

1. Insert the glass tube with a rubber film on one end into the water, as shown in the figure. During the gradual insertion, the rubber film will ( )

A． gradually convex

B． Gradually convex

C. constant

D． Hard to judge

Analysis: Since there is pressure in all directions inside the liquid, when the glass tube is inserted into the water, the lower end of the rubber membrane should be subject to upward pressure, and the further downward, the greater the pressure.

2. There is 120g of water in the cup, and the water depth is 10cm. When the area of ​​the bottom of the cup is 10cm2, what is the pressure on the bottom of the cup? What is the pressure on the bottom of the cup?

Solution: P = ρ liquid gh depth

=ρ水ghdepth

=1.0×103kg/m3×10N/kg×0.1m

=1000Pa

F=PS=1000Pa×10-4m2=1N

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"Studying the Pressure of Liquids" Magical Pressure PPT Courseware 2:

"Studying the Pressure of Liquids" Magical Pressure PPT Courseware 2 1. Surprising Experiments Activity 1 Watch the experiment imitating Pascal 2. Explore the characteristics of the internal pressure of the liquid The liquid not only exerts pressure on the bottom of the container, but also exerts pressure on the side walls of the container. Liquid creates pressure...