Name: hydraulic force transfer with pascal's law
Uploaded: 2023-04-30T11:04:28.000Z
Duration: 1 min 3 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Physics

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

9-12.P.1.4.b

Application of Pascal's Law

Hydraulic systems like the hydraulic jack are based on Pascal&#39;s law.
It consists of a U-shaped tube having columns of unequal area of cross-section. Piston A is fitted onto the smaller column, while piston B is fitted onto the larger column.
The tube is filled with a fluid such that it attains the same height in both the columns. When a force is applied to piston A, it exerts a pressure p1 on the fluid.
According to Pascal&#39;s law, this pressure is transmitted to piston B through the fluid due to which piston B is pushed outward.
The pressure p2 felt by piston B is equal to p1. Now, using the relationship between pressure and force, an expression for the forces in a hydraulic system is obtained provided that the friction in the system is negligible. The output force can be increased in the hydraulic system by applying a force on a smaller area.

application of pascal's law

Pascal&#39;s experimentally proven observations&#8212;that a change in pressure applied to an enclosed fluid is transmitted undiminished throughout the fluid and to the walls of its container&#8212;provide the foundations for hydraulics, one of the most important developments in modern mechanical technology.
Hydraulic systems are used to operate automotive brakes, hydraulic jacks, and numerous other mechanical systems. We can derive a relationship between the forces in a simple hydraulic system by applying Pascal&#39;s principle. In the system, there are two pistons at the same height, so there is no difference in pressure due to a difference in depth. The pressure due to the force acting on the smaller area is transmitted undiminished throughout the fluid and to all walls of the container. Thus, the pressure felt at the larger piston is equal to the pressure transmitted by the smaller area. This gives an equation that relates the ratios of force to area in any hydraulic system, provided that the pistons are at the same vertical height and that the friction in the system is negligible. Hydraulic systems can increase or decrease the force applied to them. To make the force larger, the pressure is applied to a larger area. For example, if a 100 N force is applied to the smaller cylinder, and the other cylinder has an area five times greater, then the output force is 500 N.
The hydraulic jack is such a hydraulic system. It is used to lift heavy loads, such as the ones used by auto mechanics to raise an automobile. A small force applied over a small area can balance a much larger force on the other side over a larger area. From Pascal&#39;s principle, it can be shown that the force needed to lift a car is less than the weight of the car.
This text is adapted from<a href="https://openstax.org/books/university-physics-volume-1/pages/14-3-pascals-principle-and-hydraulics"> Openstax, University Physics Volume 1, Section 14.3: Pascal</a>&#39;<a href="https://openstax.org/books/university-physics-volume-1/pages/14-3-pascals-principle-and-hydraulics">s Principle and Hydraulics</a>.

Pascal&#39;s experimentally proven observations&#8212;that a change in pressure applied to an enclosed fluid is transmitted undiminished throughout the ...

Education

JoVE Core

Unit 1

Fluid Mechanics

KEY TERMS AND CONCEPTS

hydraulic force transfer with pascal's law

Hydraulic force transfer uses Pascal's law to move pressure through an enclosed fluid. Pascal showed experimentally that a change in pressure applied to a confined fluid is transmitted undiminished throughout the fluid and to the walls of its container. That idea is the basis of hydraulics, a major part of modern mechanical technology.

Hydraulic systems appear in automotive brakes, hydraulic jacks, and many other machines. A simple hydraulic system uses two pistons at the same height. Because the pistons are at the same vertical level, there is no pressure change from depth. The pressure created by the force on the smaller area travels through the fluid and reaches the larger piston with the same value.

This pressure balance gives a relationship between force and area in a hydraulic system. It works when the pistons are at the same height and friction in the system is negligible. Hydraulic systems can increase or decrease the force applied to them. To increase the output force, the pressure is applied over a larger area.

For example, if a 100 N force is applied to the smaller cylinder and the other cylinder has five times the area, the output force is 500 N. A hydraulic jack uses this principle to lift heavy loads. Auto mechanics use hydraulic jacks to raise cars. A small force over a small area can balance a much larger force on the other side over a larger area. From Pascal's principle, the force needed to lift a car is less than the car's weight.

Hydraulic Force Transfer with Pascal's Law

hydraulic-force-transfer-with-pascals-law

characteristics of fluids

Fluid Behavior Under Force

Fluid behavior under force differs from the behavior of solids. When a force acts parallel to the top surface of a solid, the solid resists it because of internal friction between its layers. This is called shearing resistance. If the force is removed, the shearing forces help the solid return to its original shape. Other deformation forces can also change the shape of a solid for a short time, as long as the force stays below a threshold magnitude. Solids usually keep their shape, which makes...

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density

Density, Floating, and Specific Gravity

Density helps explain why objects sink or float in a fluid. It is also useful for identifying a substance and for learning about its phase and substructure. The SI unit of density is kg/m3, and the cgs unit is g/cm3. Liquids and solids usually have densities that are roughly comparable. That matches the fact that their atoms are in close contact. Gases have much lower densities than liquids and solids because their atoms are separated by large amounts of empty space. Density does not always...

pressure of fluids

Fluid Pressure in Everyday Life

Fluid pressure appears in many everyday situations, including blood pressure and weather systems. The same force can have a very different effect depending on the area it acts on. A force spread over 1 mm² creates 100 times more pressure than the same force spread over 1 cm². That is why a sharp needle can pierce skin with a small force, while the same force from a finger usually does not. Pressure is especially important when studying fluids. A fluid does not offer much resistance to a force...

variation of atmospheric pressure

Atmospheric Pressure and Altitude

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pascal's law

Pascal’s Principle in Static Fluids

Pascal’s principle explains how pressure changes move through a fluid that is not flowing. A fluid at rest is in static equilibrium. If the fluid is water, it is in hydrostatic equilibrium. In this state, the net force on any part of the fluid must be zero, or the fluid will begin to flow. Blaise Pascal described this idea in 1653 in Treatise on the Equilibrium of Liquids. He showed that when pressure changes in an enclosed fluid, that change is transmitted without loss through the fluid and...

Hydraulic force transfer uses Pascal's law to move pressure through an enclosed fluid. Pascal showed experimentally that a change in pressure applied to a confined fluid is transmitted undiminished throughout the fluid and to the walls of its container. That idea is the basis of hydraulics, a major part of modern mechanical technology. Hydraulic systems appear in automotive brakes, hydraulic jacks, and many other machines. A simple hydraulic system uses two pistons at the same height. Because...

pressure gauges

Gauge vs Absolute Pressure

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archimedes' principle

Buoyant Force from Fluid Pressure

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How Buoyancy Depends on Density

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Fluid Pressure in an Accelerating Elevator

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excess pressure inside a drop and a bubble

excess-pressure-inside-a-drop-and-a-bubble

Surface Tension in Drops and Bubbles

Surface tension sets the pressure difference in small drops and bubbles. For a tiny liquid drop, gravity can be neglected, so the drop is treated as spherical. It can also be viewed as two equal hemispherical drops joined together by surface tension. The forces on the drop come from three sources. The liquid inside pushes outward, the air outside pushes inward, and surface tension acts along the diameter between the two hemispheres. Since surface tension is force per unit length, it creates a...

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buoyancy

Buoyant Force in Sinking and Floating

Buoyant force explains why objects float, sink, or stay suspended in a fluid. A fluid can be a liquid or a gas, and every object placed in it experiences this upward force. A metal ball sinks, while a rubber ball floats. A submarine also changes its buoyancy to move up or down. The force comes from pressure changes in the fluid. Fluid pressure increases with depth because the weight of the fluid above also increases. That means the bottom of an object feels more pressure than the top. This...

contact angle

Wetting and Surface Curvature

Wetting and surface curvature describe how a liquid behaves where it meets a solid. When a solid is dipped into a liquid, the liquid surface can bend near the contact line. In some cases, the liquid rises along the solid. In others, the surface becomes convex or depressed near the solid. This behavior comes from cohesive and adhesive forces. Adhesive force is the attraction between molecules of different materials, such as a solid and a liquid. Cohesive force is the attraction between...

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rise of liquid in a capillary tube

Capillary Action in Thin Tubes

Capillary action explains why liquid can rise or fall in a very thin tube compared with the liquid around it. A capillary is a narrow cylindrical tube, and the effect becomes noticeable when it is dipped into a liquid. The movement happens because two forces act in opposite directions. Cohesive forces make liquid molecules stick to each other, so the liquid tends to hold together and form a rounded shape. Adhesive forces pull the liquid toward the walls of the container. In a narrow glass...

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laminar and turbulent flow

Fluid Motion Patterns in Air and Water

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Fluid Flow in Narrowing Pipes

Fluid flow in a pipe is described by flow rate and average speed. Flow rate, or volume flow rate, is the amount of fluid that passes a point through an area in a given time. It depends on both how fast the fluid moves and the size and shape of the conduit. For a river or pipe, a greater speed usually means a greater flow rate. A larger cross-sectional area also increases flow rate. That is why the same fluid can move differently through conduits of different sizes. The relationship becomes...

bernoulli's equation

Fluid Pressure and Speed in Motion

Bernoulli's equation connects fluid pressure with fluid speed. It helps explain why moving fluids can create pressure changes in everyday situations. One example is when two trains pass each other quickly and seem to pull inward. The same effect can happen when two cars pass each other at high speed. As the air between the trains or cars speeds up, its pressure drops. The air on the outside stays at atmospheric pressure. That pressure difference creates a net inward force on the vehicles.

bernoulli's principle

Fluid Pressure and Speed Changes

Bernoulli's equation links fluid pressure and fluid speed in a static, incompressible fluid. For horizontal flow, where gravitational energy density stays constant, the equation is especially useful. In that setting, the result is known as Bernoulli's principle. Bernoulli's principle says that fluid pressure drops when speed increases, and pressure rises when speed decreases. This pressure-speed relationship helps explain how moving fluids behave in simple flow situations. It also provides a...

bernoulli's principle: applications

Bernoulli's Principle in Fluid Devices

Bernoulli's principle helps explain how many fluid devices work when the fluid moves at a constant height. It is useful for devices that use fast flow to create low pressure and for devices that measure fluid speed. Some devices use this pressure change to pull one fluid into another. These are called entrainment devices. A Bunsen burner uses an adjustable gas nozzle to entrain air for proper combustion. An atomizer uses a squeeze bulb to make a jet of air that pulls perfume drops into the...

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energy conservation and bernoulli's equation

energy-conservation-and-bernoulli-s-equation

Bernoulli’s Equation in Streamlined Flow

Bernoulli’s equation describes energy in a moving fluid. It comes from the conservation of energy principle, or the work-energy theorem, applied to an incompressible, inviscid fluid in laminar, steady, irrotational flow. The equation says that pressure energy, potential energy, and kinetic energy per unit volume stay constant along a streamline. Each term has the units of energy per unit volume. The kinetic energy per unit volume is called kinetic energy density, and the potential energy per...

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viscosity

Viscosity and How Fluids Flow

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poiseuille's law and reynolds number

Fluid Resistance, Viscosity, and Flow Regime

Fluid resistance, viscosity, and flow regime shape how liquid moves through a horizontal tube. Fluid flows from high pressure to low pressure. The flow rate, Q, is the ratio of the pressure difference to the resistance in the tube. A larger pressure difference gives a higher flow rate. Poiseuille's law describes laminar flow of an incompressible fluid in a tube. In this relation, the factors that affect flow rate except pressure are grouped into resistance. Resistance depends on the tube size...

stokes' law

Terminal Velocity in a Viscous Fluid

Viscous forces act like friction in a liquid. They resist the relative motion of molecules and pull back on a solid body moving through the fluid. The size of this force depends on the body’s shape and size, its speed, and the liquid’s viscosity, density, and temperature. For a spherical solid object, the force in a fluid is described by Stokes’ law. This law applies only at low Reynolds number, when the flow is laminar and not turbulent. Experiments show that the force is proportional to the...

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key terms and concepts

See how Pascal's law explains hydraulic force transfer in brakes and jacks, with pressure passing through a fluid and changing force through area.

Hydraulic Force Transfer with Pascal's Law | JoVE K12

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Hydraulic Force Transfer with Pascal's Law

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