Pascal’s law is a very important physical phenomenon that we need to consider in different kinds of fields of engineering. For example, in hydraulic systems, the importance of this law is very significant. Here, we explain this law in detail and how it works. And also, you can find information about the application areas of this law. You will see that Pascal’s principle is very important.
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What is Pascal’s Law?
Pascal’s law states that fluid transfers the pressure that we apply on them uniformly throughout the system. So, the pressure is constant in every portion of the fluid. Also, we need to consider the hydrostatic pressures and pressure loss due to the irreversibilities. But in general, for systems that we use Pascal’s law, we neglect these effects because they are very minimal.
If we give an example of this situation, for example, we are applying 5 kg of mass to the piston system of fluid. And the total area of the piston whişch connects to the fluid is 2 cm2. According to the pressure law, the total pressure that the fluid will transfer is 2.5 kgf.cm-2. So, at every ğportion of the fluid, we will feel this effect.
To understand the mechanical advantage of this system, for example, we are using a two-side piston-cylinder system. For example, we apply 3000 kg mass to the piston system that has an area of 100 cm2. And the total pressure that we apply to the fluid is 30kg/cm2. So, at every point o the fluid, we feel this pressure value. And we want to find how many kilograms we can carry if the other piston has 10cm2. So, if we multiply the 30kg/cm2 by the 10cm2, we will find that the total mass is 300kg.
We use this relation;
In this relation, F1 is the first force that we apply to the first platform. F2 is the second force that we apply to the second platform. A1 is the area of the first platform and A2 is the area of the second platform.
So, you know already that F/A is the general equation of pressure. And you can understand that the first pressure is equal to the second pressure in the hydraulic cylinder system.
But in these systems, the movement of the big mass is much smaller than the small mass. Think about the movement of the total fluid. For example, we want to move the bigger mass with a 10 cm upward movement. The total volume of the fluid replacement must be 100cm2*10cm = 1000 cm3. So the total fluid volume movement at the smaller piston must be the same. If we divide the 1000cm3 by 10cm2 which is the total area of the smaller piston, we find that we need to move the smaller piston 10cm downward movement.
As you understand, we use these systems for the movements of the high kilograms in smaller movements.
Importance of Pascal’s Law in Hydraulic Systems
In most hydraulic systems, the use of Pascal’s principles is very important. We need to understand the general working principles of hydraulic systems.
In a typical hydraulic system, there is a pressure generator which we call the pump. The pump pressurizes the fluid in the hydraulic system and the electronic control of these systems directs this high-pressure fluid into the hydraulic system.
Think about a piston-cylinder system that carries the car or heavier systems on it. There is a pump that gives a specific pressure on the system. And the valve opens to take this high-pressure fluid inside the cylinder. And the car begins to rise. Once the inlet valve closes, the rise of the car stops. Also, there is an outlet valve. If the outlet valve opens, the platform of the car is lower because the hydraulic fluid discharges from the system. Also, the pressure of the hydraulic fluid decreases with this action.
And the hydraulic fluid goes into a container. And pump takes the fluid from the container and pressurizes it again.
This is a very simple explanation of a hydraulic system. The amount of pressure that the pump gives to a fluid and the amoung of kilograms that a platform can carry is the very important parameters here.
Also, hydrostatic pressure is a part of Pascal’s principle. According to this principle, with the increasing depth of the fluid, the pressure of the fluid increases. There is a relation that states this situation;
In this equation, ρ is the density of the fluid. g is the gravitational acceleration and h is the depth of the fluid. So, the depths of the oceans have very high pressures that we can not stay live in these pressures.
Applications That We Use Pascal’s Principle
There are different kinds of applications in which we use Pascal’s law. You will see that Pascal’s law is very useful stuff in most engineering systems.
Pascal’s Law in Braking Systems
If you take a look at the braking systems of automotive applications, most of them have fluids inside them. So, there is a hydraulic system and the application of Pascal’s principle is very important here.
Once you press the brake pedal of an automobile, the fluid inside the brake hoses and tubes gets ğressurize. The fluids transfer this pressure to the brake discs. And discs move to press the wheels of the car to stop it. The movement of the brake pedal is higher than the disc movement in general. So, the total force at the disc is much higher than the total force that you apply to the brake pedal.
In modern systems, there are brake pumps that increase the total force on the discs. Once you press the brake pedal, the high-pressure fluid is released through a valve and stops the car.
Pascal’s Law in Hydraulic Presses
You have probably seen lots of videos of hydraulic presses on social media. So, these presses are squeezing all the objects and break into pieces nearly all the materials with their very high forces and presses.
We obtain these high forces in hydrauşic presses with Pascal’s law also. In these systems, the pumps are very strong and pressurize the fluid at very high levels. And also, you probably see, that the total velocity and the movement of the presses are very slow. This means it carries very high pressures and forces just like the example of the car lifting systems.
So, once the operator opens the inlet valve, the press begins to apply the pressure.
Hydraulic presses are very important applications in industry.
Hydraulic Plastic Injection Machines
They are also very important applications in the production of plastic materials and parts. In plastic injection processes and machines, the use of hydraulic systems is very common.
Because we require very high pressures to inject the plastic inside the molds. And we need clamping force to close these mold halves. This closing action is generally made with hydraulic systems.
A hydraulic system and pressure close the halves and keep them tight with Pascal’s rule.
Construction Equipment; Bulldozers, Excavators…
They are also very important examples of Pascal’s law. Because they are hydraulic systems again.
If you take a look at the construction equipment, they include very complex hydraulic systems to work well. And they can move very heavy boulders and soils with their very high strength.
Their ladles are moving with the application of high-pressure fluids. There are cylinder systems that move the ladles and arms hydraulically. And the hydraulic pump takes its power from the internal combustion engine that they have.
The operator gives the commands for which valve will open and close for the movement of the ladles in the intended motions. There are sticks the operator controls the machine. These sticks control the movement of the ladles.
Pascal’s Law in Hydraulic Cranes
Hydraulic cranes are also a very important example that we use this law. They are so important systems that we lift our cars to change the tires. You can remember that we need to push the rod permanently to lift the car. And with each push, the car lifts a little bit. So, with this rod, we pump the fluid inside the cylinder that lifts our car.
There are lots of kinds of submarine applications that we use to view the depths of the ocean. These submarine vehicles have very high mechanical strength to withstand the high pressures that they will see in the depths of the ocean. So, engineers are designing these vehicles with special care by calculating the hydrostatic pressures of the depths of the ocean.
Water Towers and Dams
These are also very important examples of how we calculate the effects of high hydrostatic pressures. They build water towers at high elevations in the residential areas. So, the water that comes to the faucets and taps of the homes from this tower is very high pressure. And the water can flow through these faucets because of the high elevation of the towers.
Also, in the design of the dams, we generally calculate the effect of the hydrostatic pressure of the accumulating water on the dam wall. So, the hydrostatic effect has a very important effect on the walls that engineers must calculate.
As you see above, Pascal’s law has a very big importance in engineering applications. We need to consider all the important things about Pascal’s law while we are designing our systems.
The statements of Pascal’s law are very simple. The fluid transfer the same pressure over them. If you apply pressure to a fluid, the same pressure will be applied by the fluid to the other sections of the system.
There are also lots of kinds of applications of Pascal’s principle. Most of these applications are hydraulic systems. In hydraulic systems, we use the pressure transfer feature of the fluid.
For example, in the braking systems of automobiles, the ladles of the excavators, industries manufacturing equipment… They are the general applications that we use in Pascal’s law.
Finally, these are the general points about Pascal’s principle.
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FAQs About Pascal’s Principle
According to this principle, the fluid will transfer all the pressure that we apply to that fluid from a section. In every section of the fluid, this pressure is the same. So, if we apply pressure from a cylinder that has contact with the fluid, this cylinder will transfer the pressure to the other sections of the fluid.
There are lots of kinds of practical applications of this law. For example, hydraulic cranes and hydraulic lift machines are very important applications. With the application of small and frequent forces, we can lift a very high weight with Pascal’s principle.
The best description of Pascal’s principle, if we exert pressure on a fluid, the fluid will transfer the same pressure to all the portions of the fluid. So, we can transfer the pressure with the use of fluids.
There are lots of kinds of engineering applications in which we use this principle. For example, lots of production systems are made according to Pascal’s law. And other kinds of engineering systems are very important. The example above shows the importance of this principle.
If we need to give three application examples of Pascal’s law, they can be hydraulic brakes, hydraulic lifts, and hydraulic presses. They are very important practical applications that we use in Pascal’s law.
No, we can not use this law for gases. Because, gases are compressible and for compressible fluids, the use of this law will not be true. If we apply pressure to gas or compressible fluid, the fluid becomes compressed and the density of the fluid increases. So, we will not see the same pressure effect of this fluid on the other sides.