Pascals Principle: Pressure in Enclosed Fluids Explained

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In summary: The slave piston will exert a force directly proportionate to the amount of liquid that has been transferred.
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Celluhh
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Can someone explain why pressure is transmitted equally to all parts of an enclosed fluid, as stated in pascals principle ? Why doesn't the 'pressure increases with height' rule play a part ? Is it because the volume of the liquid will always stay the same? But then so what ?
 
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  • #2
Celluhh said:
Can someone explain why pressure is transmitted equally to all parts of an enclosed fluid, as stated in pascals principle ? Why doesn't the 'pressure increases with height' rule play a part ? Is it because the volume of the liquid will always stay the same? But then so what ?

These are two separate issues and they appear very regularly here. I don't think there is a problem if you deal with them one at a time and there is no conflict. Take a volume of fluid way out into microgravity conditions. The pressure will be transmitted evenly throughout. Why? Because if it were not equal everywhere, the fluid would be constantly flowing around and the pressure would relate to the actual shape of the container (not a reasonable suggestion).

Once you get down on Earth, there are other forces at work and the principle only applies, strictly, in an infinitessimally small volume. The weight of the fluid above will be causing the pressure and it's quite reasonable to explain this in terms of the density, height of column above and g.

If you take an imaginary surface, between one region and another in a contained fluid, the pressure must be the same in each direction, when equilibrium has been reached - just the same as pressure on the walls of the container.
 
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I still don't get how they link.
 
  • #5
The pressure varies with position within the enclosure, but at any given location, it is measured to be the same in all directions. If you swim to the bottom of a swimming pool, the pressure on your ear drum is the same whether your head is erect, or whether your ear is pointing toward the bottom of the pool, or whether you ear is pointing toward the surface. A parameter that does not depend on direction at a given spatial location is said to be isotropic, meaning independent of direction.
 
  • #6
Oh so you are saying that pressure at same level is the same , but at different levels in the enclosed fluid the ' pressure increases with height' rule still applies?
 
  • #7
Celluhh said:
Oh so you are saying that pressure at same level is the same , but at different levels in the enclosed fluid the ' pressure increases with height' rule still applies?

yes.
 
  • #8
So the pressure exerted by the master piston is the pressure that acts on the slave piston to produce a force to lift the load right ? Without the force applied at the master piston nothing would happen right ?
But what happens if there is loquid transfer? what will be the force exerted at the slave piston, and how do we calculate it ?
 

What is Pascal's Principle and how does it relate to pressure in enclosed fluids?

Pascal's Principle states that pressure applied to a confined fluid is transmitted equally in all directions. This means that if pressure is applied to one point in a fluid, it will be distributed evenly throughout the entire fluid. This principle is important in understanding the behavior of fluids in enclosed systems, such as hydraulic systems.

How is pressure measured in fluids?

Pressure in fluids is typically measured in units of force per unit area, such as pounds per square inch (psi) or pascals (Pa). The force is typically exerted by the weight of the fluid itself or by an external force, and the area is the surface on which the force is acting. In order to measure pressure, a pressure gauge is used, which converts the force into a readable numerical value.

What are some examples of Pascal's Principle in everyday life?

Pascal's Principle is commonly observed in hydraulic systems, such as car brakes and hydraulic lifts. In these systems, a small force applied to a small area is able to generate a larger force on a larger area, due to the transmission of pressure through the enclosed fluid. Other examples include the functioning of water guns, syringes, and hydraulic jacks.

What factors can affect the pressure in a fluid?

The pressure in a fluid can be affected by several factors, including the depth of the fluid, the density of the fluid, and the acceleration due to gravity. As the depth of a fluid increases, the pressure at the bottom also increases due to the weight of the fluid above. Similarly, as the density of the fluid increases, the pressure also increases. The acceleration due to gravity also affects the pressure, as it determines the weight of the fluid and the force applied to the area.

What are the limitations of Pascal's Principle?

While Pascal's Principle is a useful concept in understanding the behavior of enclosed fluids, it does have some limitations. One limitation is that it only applies to fluids that are incompressible, meaning their volume does not change under pressure. Additionally, it assumes that there are no external forces acting on the fluid, which may not always be the case. Finally, it does not take into account the effects of friction and turbulence in the fluid, which can also impact the pressure and behavior of the fluid.

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