"Pressure" Pressure PPT

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"Pressure" Pressure PPT

Part One: Preview Perception

1. Explore the influencing factors of stress effects

1. Exploration method: Control variable method.

2. Research conclusion: It is related to the size of the pressure and the stress area.

(1) The force-bearing area is certain. The greater the pressure, the more obvious the effect.

(2) When the pressure is constant, the smaller the force-bearing area, the more obvious the effect will be.

2. Pressure

1. Concept: The ratio of the pressure on an object to the force-bearing area.

2. Formula: p=F/S.

(1) Meaning: Pressure is numerically equal to the pressure per unit area of ​​an object.

(2) Various physical quantities and their units

3. Increase and decrease pressure

Pressure PPT, Part 2: Interactive Classroom Understanding

understanding of pressure

(1) Calculation formula: p=F/S.

①F represents the pressure exerted on the object, and the direction of the pressure is perpendicular to the surface of the object. An object placed vertically on a horizontal surface without any other force exerts pressure on the support surface equal to the object's gravity.

②S is the force-bearing area, which refers to the area where two objects are in contact with each other.

③p is pressure, 1 Pa means that the pressure on the surface of an object of 1 m2 is 1 N.

(2) Increase and decrease in pressure: When judging the increase and decrease in pressure, changes in the two factors of pressure and stress area must be considered at the same time, and the change in pressure is judged according to the formula p=F/S.

(3) Expansion: The pressure generated by a cylinder with uniform mass is large.

The pressure of a cylinder with uniform mass placed on the horizontal surface on the horizontal surface is F=G, and the pressure of the cylinder on the horizontal surface is p=F/S=G/S=mg/S=ρVg/S=ρgh.

[Example] Electric vehicles are a new type of transportation that is being vigorously promoted. They are energy-saving and environmentally friendly. The picture below shows an electric car parked on a level ground. The mass is 1.6×103 kg. The contact area between each tire and the ground is 2×10-2 m2. g is 10 N/kg. beg:

(1) The pressure of the car on the ground; (2) The pressure of the car on the ground.

Answer (1) The pressure of the car on the ground

F=G=mg=1.6×103 kg×10 N/kg=1.6×104 N.

Pressure PPT, Part 3: Try the application

1. The effect of pressure

1. Xiao Min used a sponge, table and weights to conduct an exploratory experiment as shown in the picture. Which of the following analysis of the entire inquiry activity is incorrect ()

A. Question of inquiry: What factors are related to the effect of stress?

B. Exploration method: control variable method

C. Analysis of the exploration process: Determine the stress effect by observing the size of the sponge depression area

D. Conclusion of the investigation: The effect of pressure is related to the size of the pressure and the size of the force-bearing area.

In the picture, the dent degree of the sponge is used to represent the effect of pressure. Putting the table upright or upside down changes the force-bearing area of ​​the sponge. Adding weights can change the pressure on the sponge. Explore what factors are related to the effect of pressure, so A Correct, C is incorrect. The factors that affect the pressure effect include pressure and stress area. When exploring the relationship between the pressure effect and one of the factors, the control variable method should be used to control the other factor unchanged, so B is correct. It can be seen from the pictures A and B in the title that the stress-bearing area of ​​the sponge is constant. The pressure on the sponge in Picture B is relatively large, and the depression of the sponge is large. This means that when the stress-bearing area is constant, the greater the pressure, the more obvious the effect of pressure; from It can be seen from pictures B and C in the question that the pressure on the sponge is certain. The sponge in picture B has a smaller stressed area and the effect of pressure is obvious. This means that when the pressure is constant, the smaller the stressed area, the more obvious the effect of pressure, so D is correct. .

2. In the activity of exploring the factors related to the effect of stress, the students first conducted heated discussions and bold conjectures, and then designed a variety of verification schemes. Xiao Ming performed the operation as shown in Figure A. He felt that the pressure on his left thumb was much stronger than that on his right thumb; and the harder he applied, the more obvious the pressure felt. Xiaodong’s experiment is shown in Figure B. He observed that the deformation of the part of the balloon that was in contact with the palm was small, while the part of the balloon that was held up by his fingers deformed significantly; and the greater the force exerted by the fingers, the more obvious the deformation.

After the experiment, the students communicated with each other and came to the following conclusions:

(1) When the pressure is the same, ______________, the effect of pressure is more obvious.

(2) When the stressed areas are the same, ______________, the effect of pressure is more obvious.

(3) In physics, the effect of pressure is expressed by the physical quantity _______.

The effect of pressure is related to the size of the pressure and the size of the force-bearing area. The greater the pressure, the smaller the force-bearing area, and the more obvious the effect of pressure. In physics, pressure is used to express the effect of pressure.

2. Pressure

3. Which of the following statements is correct ()

A. The greater the pressure, the greater the pressure must be

B. The smaller the force-bearing area, the greater the pressure must be

C. The force-bearing area remains unchanged. The greater the gravity of the object, the greater the pressure must be.

D. The pressure remains unchanged, and the larger the force-bearing area, the smaller the pressure must be.

4. The pressure generated by the London Olympic mascot on the horizontal surface is about 16 000 Pa, and its physical meaning is ____.

3. Methods of increasing and decreasing pressure

5. In the example shown in the figure, the one that increases the pressure is ()

6. Antarctica is the coldest place on earth. As shown in the picture, the Chinese scientific expedition team members unloaded a Caterpillar vehicle on thin ice. The vehicle mass is 2.5×104 kg, and the total contact area between the track and the ground is 2.5 m2. (g is taken as 10 N/kg)

(1) In order to move this car, planks were laid on the ice to __________.

(2) What is the pressure of this car on the wooden board?

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Update Time: 2024-11-18

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