Name: buoyant force from fluid pressure
Uploaded: 2023-04-30T11:04:43.000Z
Duration: 1 min 13 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

Archimedes' Principle

Consider an object at rest, completely immersed in a fluid. It displaces an equal volume of fluid to occupy that space.
An upward buoyant force keeps the object stationary.
If the object is removed from the fluid, the space gets filled by the same volume of fluid earlier displaced by it.
This fluid volume is now acted upon by the same buoyant force earlier acting on the object. Since the fluid volume is at rest, the buoyant force is balanced by its weight.
Thus, the magnitude of the buoyant force acting on an object in a fluid equals the weight of the fluid displaced by it. This is known as Archimedes&#39; Principle.
Mathematically, the buoyant force is equal to the product of mass of the fluid displaced and the acceleration due to gravity.
Using the relationship between mass and density, the buoyant force can also be represented as the product of density of fluid, volume of displaced fluid, and the acceleration due to gravity.

archimedes' principle

Archimedes&#39;&#160;principle states that an upward buoyant force exerted on a body that is immersed partially or entirely in a fluid is equal to the weight of the fluid displaced by it. To understand how much buoyant force is needed to make an object float, let us think about what happens when a submerged object is removed from a fluid. If the object were not in the fluid, the space occupied by the object would be filled by the fluid having a weight wfl. This weight is supported by the surrounding fluid, so the buoyant force must equal to wfl, the weight of the fluid displaced by the object.
This principle is named after the Greek mathematician Archimedes (ca. 287&#8211;212 BCE), who stated this principle long before the concepts of force were well established. Archimedes&#39;&#160;principle refers to the force of buoyancy that results when a body is submerged in a fluid, whether partially or wholly. The force that provides the pressure of a fluid acts on a body, perpendicular to the surface of the body. In other words, the force due to the pressure at the bottom is pointed up, while at the top, the force due to the pressure is pointed down; the forces due to the pressures at the sides are pointing into the body. Since the bottom of the body is at a greater depth than the top of the body, the pressure at the lower part of the body is higher than the pressure at the upper part. Therefore, a net upward force acts on the body. This upward force is buoyancy.
This text is adapted from<a href="https://openstax.org/books/university-physics-volume-1/pages/14-4-archimedes-principle-and-buoyancy"> Openstax, University Physics Volume 1, Section 14.4: Archimedes&#8217; Principle and Buoyancy. </a>

Archimedes&#39;&#160;principle states that an upward buoyant force exerted on a body that is immersed partially or entirely in a fluid is equal to the ...

Education

JoVE Core

Unit 1

Fluid Mechanics

KEY TERMS AND CONCEPTS

buoyant force from fluid pressure

Archimedes' principle explains buoyant force in a fluid. An upward buoyant force acts on an object that is partially or fully immersed in a fluid. This force is equal to the weight of the fluid displaced by the object.

To see why an object floats, imagine removing a submerged object from the fluid. The space it occupied would be filled by fluid with weight w_fl. That weight is supported by the surrounding fluid, so the buoyant force must match the weight of the displaced fluid.

The principle is named for the Greek mathematician Archimedes, who lived around 287 to 212 BCE. He stated the idea long before the modern concept of force was fully developed. The same principle applies whether the body is only partly submerged or completely under the fluid.

Fluid pressure creates the buoyant force. The pressure force acts perpendicular to the surface of the body. The force at the bottom points upward, while the force at the top points downward. Forces at the sides point inward.

Because the bottom of the body is deeper than the top, the pressure is greater lower down than higher up. This difference creates a net upward force on the object. That upward force is buoyancy.

Buoyant Force from Fluid Pressure

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

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pressure of fluids

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pascal's law

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Archimedes' principle explains buoyant force in a fluid. An upward buoyant force acts on an object that is partially or fully immersed in a fluid. This force is equal to the weight of the fluid displaced by the object. To see why an object floats, imagine removing a submerged object from the fluid. The space it occupied would be filled by fluid with weight w_fl. That weight is supported by the surrounding fluid, so the buoyant force must match the weight of the displaced fluid. The principle...

density and archimedes' principle

How Buoyancy Depends on Density

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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...

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energy conservation and bernoulli's equation

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key terms and concepts

Learn how fluid pressure creates buoyancy and why the upward force on a submerged object equals the weight of the fluid it displaces.

Buoyant Force from Fluid Pressure | JoVE K12

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Buoyant Force from Fluid Pressure

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