Pressure transmission with liquids and gases. Law Pascal Presentation to the lesson in physics (Grade 7) on the topic
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Law of Pascal »The topic of the lesson" Pressure transmission by liquids and gases.
The purpose of the lesson: to formulate the law of Pascal. Experienced by proving the transfer of pressure of liquids and gases in all directions.
New concepts of Pascal law, hydrostatic pressure, hydrostatic pressure formula.
Let's remember: what depends on the pressure of solids to the surface? The pressure of solid bodies on the surface depends on the pressure force and the support area
Test on the topic "Pressure of solid bodies" 1. What physical value is determined by the formula P \u003d F / S C) work; Y) pressure; E) speed; O) Path. 2. Which of the listed units is the main unit of pressure measurement unit? And) watt (W); C) Joule (J); C) Newton (H); P) Pascal (PA) 3. There are two bricks of the same mass and size 1 2 Which of the bricks has a smaller pressure? A) 1; C) 2; G) the pressure is equally.
The correct answer to the test Question 1 2 3 Reply U R a
The pressure of the solid to the surface of Pascal 1 Pa \u003d 1 N / m²
Experimental task 1. Inflate the balloon. Why does the ball increase its volume?
Conclusion: The gas pressure on the ball wall is caused by the blows of the gas molecules and is directed in all directions in the same way.
Why are ball balls and soap bubbles round? The gas pressure on the walls of the vessel (and on the body placed in the gas) is caused by the blows of the gas molecules.
Gas presses on the walls in all directions equally!
From which the gas pressure depends will deliver the experiment. Take two syringe and two balloons. Fill one syringe by air, another helium. Influence balls using syringe data.
From what depends the gas pressure of air helium ρ \u003d 1.29 kg / m³ ρ \u003d 0.18 kg / m³
This experiment confirms that gas pressure depends on its density: the volume of gas in the balls is the same, but the air density is greater and the air ball is swept more, because the pressure also increases.
The magnitude of the gas pressure depends on the number and strength of the blows of molecules per unit surface
From the temperature from the concentration (the number of particles per unit volume), the gas pressure depends on ...
Experience with a bowl of Pascal
The law of Pascal Pressure produced on liquid or gas is transmitted unchanged into each point of the volume of liquid or gas.
Blaze Pascal (1623-1662) - French scientist, philosopher. He opened and investigated a number of important properties of liquids and gases, interesting and convincing experiments confirmed the existence of atmospheric pressure.
Experimental task 2 No! Liquids are incompressible: pressed by one part of the fluid, this pressure is transmitted to all other parts. Was it possible to squeeze water?
Talk to a little: how are solid bodies from liquids and gases from the point of sight of physics? Answer: Location of molecules 2. What is the peculiarity of the behavior of gas and liquid molecules? Answer: Mobility 3. What is the pressure of the gas or liquid creates? Answer: blow molecules of gas or liquid about the wall of the vessel. 4. How does gas or liquid presses on the walls of the vessel? Answer: in all directions the same
1. We inflate soap bubbles. Why do they acquire the shape of the ball? 2. Why is the burst of the projectile under water are destroyed for the living organisms living in water? 3. Why do deep-water fish when pulling them on the surface of the swimming bubble sticks out from the mouth?
Check yourself! An evil gin, located in a gaseous condition inside a closed bottle, has a strong pressure on its walls, bottom and cork. What is jean jam in all directions, if there is no hands or legs in a gaseous state? What law allows him to do this? Answer: Molecules, Pascal Law. 2. For cosmonauts, food is made in a semi-liquid form and placed in tubes with elastic walls. What helps astronauts to squeeze food from tubes? Answer: Pascal 3 law. How easier to remove a dent from the ball for table tennis? Answer: Heat, for example, throw in hot water.
Let's sum up the lesson: let's remember what they did today in the lesson, what did you know? How do liquid and gases transmit pressure? What law explains the transmission of pressure by liquids and gases? How does Pascal Law read? What technical devices are the law of Pascal? We'll see? \u003d\u003d\u003e
Pascal law is based on the device of many mechanisms. See drawings remember! Hydraulic presses
2. Hydraulic lifts The purpose of the movable cylinder is an increase in the height of the piston lift. To lower the cargo, the crane opens.
3. Filling units The filling unit for the supply of tractors flammable is true: the compressor pumps the air into a hermetically closed tank with a flammable, which in the hose enters the tractor tank.
4. Sprayers in sprayers used to combat agricultural pests, the pressure of the air is injected into the nucleus solution - 500 000 N / m2. The liquid is sprayed when the crane is open.
5. Water supply systems Pneumatic water system. The pump is supplied to the tank water compressing the airbag, and turns off when the air pressure is reached 400 000 N / m2. Water in pipes rises into rooms. When the air pressure decreases, the pump is again turned on.
6. Water jet water homes that emitted by a waterman under pressure of 1,000,000,000 n / m2, punches the holes in metal duals, shakes the breed in mines. Hydrophushki is equipped with modern fire fighting equipment.
7. When laying pipelines, the air pressure "sweels" pipes made in the form of flat metal steel tapes welded along the edges. This greatly simplifies the gasket of pipelines of various purposes.
8. Pneumatic pipelines Pressure at 10,000 - 30 000 N / m2 operates in pneumocontaine pipelines. The speed of the compositions in them reaches 45km / hour.
Verification work 5.
Comparison of the pressure of solids, gases and liquids Questions for comparison Solid bodies of gases of liquid Cause of pressure from which the estimated formula is transmitted in which direction
Homework: finish Table §36, answer questions. Exercise 14 on page 88. Objects №1.2. Experimental task: on the side wall of a high can be a nail of the holes at altitudes 3 cm, 6cm, 9cm. Place the jar in the sink under the water tap, open so that the volume of water entering the bank and the resulting out of her was the same. Track out the rods of water flowing from the holes of the banks, and make a conclusion.
Self-analysis leaf (need to emphasize) I feel inspiration, depression. Interesting, uninteresting. Not tired (la), tired (la). Satisfied (satisfied), dissatisfied (unhappy). Caused difficulties (listed) ......
New knowledge today we received in accordance with the method of scientific knowledge: observations \u003d\u003e hypothesis \u003d\u003e experiment \u003d\u003e output. You are great!
Thanks for the job!
Questions 1. What properties of gases are distinguished from solid bodies and liquids? Answer: Gases do not have their own form and permanent amount. They take the shape of the vessel and completely fill out the volume provided to them. 2. How explains the gas pressure on the basis of the teachings on the movement of molecules? Answer: Gas pressure on the walls of the vessels is caused by the blows of the gas molecules. 3.Why pressure of gas increases in compression and decreases when expanding? Answer: The number of molecules in each cubic centimeter increases with compression (decreases when the expansion decreases) from this, the number of shocks about the vessel wall increases (decreases). Consequently, the pressure increases in compression and decreases with expansion. 4. In what condition gas produces greater pressure: in cold or heated? Answer: Gas pressure in a closed vessel is the greater, the higher the gas temperature. 5.Well compressed gases contain in special cylinders? Answer: Compressed gases have a huge pressure on the walls of the vessel, so they have to enter into special durable steel cylinders.
Pascal Blaz () opened and investigated a number of important properties of liquids and gases. Since experiences confirmed the existence of atmospheric pressure, open by Italian scientist torch.
Plan for studying the physical law 1.Mathematical recording and verbal wording. Mathematical recording and verbal wording. 2. Specific confirmation. Surface confirmation. 3. Theory explains the law. Theory explains the law. 4.Rans of applicability. 5. Practical significance of the law and the scope of its application. Practical significance of the law and the scope of its application.
The theory Explaining the law Theory explaining the physical content of this law is that fluid or gas molecules are very mobile. They are always quite evenly distributed throughout the volume, and any external pressure can only be changed by the concentration of particles, and the uniformity in their distribution remains. Only at the initial moment, for example, with a decrease in the volume of gas, its density will be larger in the zone of the piston, but due to the random movement of molecules, the concentration is very quickly aligned.
The practical significance of the Pascal law in the figure shows the device of a pneumatic brake of the railway car. Mainer 1, brake cylinder 4 and tank 3 are filled with compressed air. When opening the stop crane, compressed air leaves the main pipe. And the pressure on the right side of the brake cylinder becomes less than in the left (of which compressed air due to the valve 2 cannot exit). As a result, the brake cylinder piston moves to the right and presses the brake block 5 to the rod of the wheel 6, which is slowed down.
Practical significance of the Law of Pascal The device of a jackhammer is shown in the figure. The hose 1 serves compressed air. A device 2, called a spool, directs it alternately into the upper, then into the lower part of the cylinder. Under the action of this air, the batter 3 begins to move quickly in one, then in the other direction, periodically affecting the peak 4. The latter blows are used to break the frozen soils, chopping from the massif of rocks of rocks, coal.
Slide 2.
Today at the lesson ...
1 Why does gas give? 2 What does the gas pressure depend on? 3Kak gas transfers pressure?
Slide 3.
Reiteration
Pa Formula Pressure Calculation Unit Press Pascal Blaze 1623 -1662
Slide 4.
Which of the three identical bars makes greater pressure on the table?
Slide 5.
New Material
Why does the ball increase its volume? Conclusion: gas pressure on the walls of the loan and the body placed in gas is caused by the blows of the gas molecules.
Slide 6.
What does gas pressure depend on?
Conclusion: from gas temperature from gas occupied by gas.
Slide 7.
How are gases and liquids transmit pressure?
The Law of Pascal Liquid and Gaza transmit pressure in all directions equally.
Slide 8.
Reply to questions ...
Figures 1, 2 and 3 indicate the round holes tightened with the same rubber films. When the piston moved from the position A.K. Position in, the films curved out. On what out of the drawings
Slide 9.
In one vessel there is a metal cube, in the other - water. How will these bodies produce pressure on them? The vessel is tightly closed by a plug in which two tubes are inserted. If you look into the tube a, then the vocabulary of the pipe club is poured out of the vessel. Will it take water from the tube a, if you pour into the tube b?
Slide 10.
In the vessel under the piston is gas. The piston moved from the position A to the position in the same time the gas pressure on the vessel walls at points 1, 2, 3, 4 and 5 increased?
Slide 11.
If you shoot an egg from the fine-caliber rifle, a hole is formed in it. If you shoot raw, it will split. How to explain this phenomenon? Why is the explosion of a projectile under water are destroyed for living organisms living in water? Why is a soap bubble shape a ball?
- MOU "Krasnovidovskaya Main Community School" of the Krasnovidovsky Rural settlement of the Kamsko-UStinsky Municipal District of the Republic of Tatarstan
- Lesson In physics in grade 7 on the topic "Pressure Gas
- Pressure transmission with liquids and gases.
- Pascal Law "
- Physics! What is the Capacity of the Word!
- Physics - not just sound for us!
- Physics - support and base
- All without exception to science! "
- 2. How will the gas pressure change if he is heated at a constant volume?
- a) will not change; b) will become more;c) will become less.
- 3. Rubber ball, squeezing with hands, deformed. Whether changed:
- weight - weight - volume – density – pressure - Air in it? (Write yes or not.)
- 4. Gas located in a vessel, puts pressure on the left wall equal to 300 Pa. What pressure produces gas to the bottom, upper and right vessel walls?
- a) to the lower 400 pa, on the upper 300 pa, on the right 200 pa; b) on the lower 300 pa, on the upper 100 pa, on the right 400 pa; in) .
- 5. The main reason for the pressure of the gas on the walls of the vessel is
- but) ; b) a little mutual attraction of gases molecules; c) Very small dimensions of gases molecules.
- 1. With a constant mass with a decrease in the gas volume of its pressure
- b) increases;
- 2. How will the gas pressure change if he is heated at a constant volume?
- b) will become more;
- 3. Rubber ball, squeezing with hands, deformed. At the same time changed:
- volume –
- density – pressure –
- 4. Gas located in a vessel, puts pressure on the left wall equal to 300 Pa. What pressure produces gas to the bottom, upper and right vessel walls?
- in) equally in all directions.
- 5. The main reason for the pressure of the gas on the walls of the vessel is
- but) blowing gas molecules about vessel wall;
- Pressure transfer
- liquids and gases.
- Pascal law.
- Pressure produced
- on liquid or gas,
- transferred in all
- directions without
- and z m e n and y.
- - Blaze Pascal - French mathematician and physicist, one of the minds of the XVII century. Father Pascal, Etienne, the connoisseur of mathematics and astronomy engaged in his formation. A miracle child Bellard from 12 years old began to engage in science. Father began to take him to the meetings of the scientific circle. The boy's intellect quickly developed and soon he discussed scientific problems with large scientists. At the age of 16, he wrote a wonderful "experience of conical sections." He opened and investigated a number of important properties of liquids and gases, the existence of atmospheric pressure proved interesting experiments. Its name is called a pressure unit and a popular programming language. The discoveries made by a brushing Pascal 300-years ago, we study now.
- Blaise Pascal
- (1623 - 1662)
- The structure of solid bodies, liquids and gases r and z l and h n o!
- Particles solid
- body only
- oscillating near
- equilibrium
- do not move
- by body.
- Fluid flow
- and its layers are easy
- displays relatively
- each other.
- Gas particles
- easy and easy
- robbed
- we are moving around the volume
- Therefore, they differently
- transmitted
- on them from the outside pressure.
- What is the difference?
- transmit liquids and gases
- rendered on them
- external pressure?
- Pascal law
- Liquids and gases transmit pressure in all directions equally.
- Free mobility
- liquid and gases particles
- leads to alignment
- pressure Press
- n and P A V L E N I M M!
- Pascal law
- Stand on one leg,
- Another
- Rose on tiptoe,
- made out
- As has changed
- pressure on the floor?
- Well done!
- Sit down.
- Figures 1, 2 and 3 indicate the round holes tightened with the same rubber films. When the piston moved from the position A to the position in, the films were arched out. On what out of the drawings
- In one vessel there is a metal cube, in the other - water. How will these bodies produce pressure on them?
- In the vessel under the piston is
- gas. Piston moved out
- provisions and to position in
- Whether the equally increased when
- this gas pressure on the walls
- Vessel at points 1, 2, 3, 4 and 5?
- Think
- and about t in e m!
- If the fine-caliber rifle is shooting into the boiled rifle
- egg, the hole is formed. If you shoot raw
- egg, it will split. How to explain this phenomenon?
- Will it
- toothpaste squeezed out of
- tube under conditions
- weightlessness as well as in
- normal conditions?
- Why an explosion
- shell under water
- doodle for all
- living in water
- organisms?
- Why
- bubble
- acquire
- form
- bowl?
- Pressure \u003d Pressure force / Support area
- p \u003d FD / S
- Sign up text from fragments A, B, B, G:
- If known ...
- A. 1 ... Pressure and Support Square, ...
- 2 ... Pressure force and pressure, ...
- 3 ... Pressure power and support area, ...
- then you can calculate ...
- B. 1 ... Pressure ...
- 2 ... Pressure power ...
- 3 ... Square support ...
- according to the formula:
- B. 1 ... FDD / S. 2 ... P * S. 3 ... FD / P
- Unit of measurement will be:
- G. 1 ... N. 2 ... m2. 3 ... PA.
- Check the answer: A1 B2 B2 G1; A2 B3 B3 g2; A3 B1 B1 g1.
- P * S.
- p \u003d FD / S [p] \u003d [n / m2] \u003d [Pa]
- Make the text from fragments A, B, B, g.
- A. 1. Pressure in liquids and gases ...
- 2. Pressure in solid bodies ...
- B. 1. Transferred in the direction of the current force.
- 2. Transmitted in all directions equally.
- B. 1. This property of solid bodies is due to the fact that ...
- 2. This property of liquids and gases is associated with ...
- G. 1. Their molecules can move throughout
- directions.
- 2. Their molecules only fluctuate
- equilibrium.
- ANSWER: A1B2B2G1; A2B1V1G2
- 1. The gas pressure on the vessel walls and the body placed in the gas is caused by the blows of the gas molecules.
- 2. The gas pressure depends on the temperature and on the volume of the gas occupied by this mass.
- 3. Liquids and gases transmit pressure in all directions equally.
- § 35, 36
- Exercise 14.
In our experience, moving gas molecules continuously hit the ball wall inside and outside. When pumping air, the number of molecules in the bell around the ball decreases. But inside the knotted ball, their number does not change. Therefore, the number of blows of molecules about the outer walls of the shell becomes less than the number of shocks about the inner walls and the ball is blown up until the force of the elasticity of its rubber shell becomes equal to the power of the gas pressure. The ball shape that the bloated sheath takes, shows that the gas presses on its machines in all directions equally, in other words, the number of blows of molecules occurring on each square centimeter of the surface area, in all directions equally. The same pressure in all directions is characteristic of gas and is a consequence of the erratic movement of a huge number of molecules. So, with a decrease in the volume of gas, its pressure increases, and with an increase in the volume, the pressure decreases.
