Name: how buoyancy keeps bodies stable in water
Uploaded: 2025-02-13T15:43:11.000Z
Duration: 1 min 11 s
Channel: JoVE

静止した物体が完全にまたは部分的に流体に沈むと、流体は浮力と呼ばれる力を物体に及ぼします。
この力は、浮力の中心と呼ばれる点を通じて作用します。
浮力は、体によって押しのけられた流体の重量に等しく、垂直に上向きに作用する、この現象はアルキメデスの原理として知られています。
物体は、変位した後に元の位置に戻る場合、安定した平衡状態にあり、それがその安定性を定義します。
体が傾くと、浮力の中心が移動し、体の軸がメタセンターと呼ばれる新しい浮力の中心を介して垂直線と整列し、体の安定性を決定します。
完全に水没した物体は、重心が浮力の中心より下にある場合、小さな回転中に安定した平衡を保ちます。
浮体が傾くと、重心が浮力の中心より上にある場合でも、浮力が移動して重りと復元カップルを形成します。
しかし、背が高くて細い体は、夫婦が転倒し、不安定になる可能性があります。

水中および浮体の浮力と安定性

Buoyancy and Stability for Submerged and Floating Bodies

流体力学では、浮力と安定性は水中および浮体の挙動を理解するための重要な概念です。静止物体が流体に完全にまたは部分的に浸っている場合、流体は物体に浮力と呼ばれる力を及ぼします。この力は、浮力の中心と呼ばれる点、つまり押しのけられた流体の体積の中心を通って垂直に上向きに作用します。アルキメデスの原理によると、浮力の大きさは物体によって押しのけられた流体の重量に等しくなります。

 流体中の物体の安定性は、移動後に元の位置に戻る能力に依存します。水中物体の場合、安定性は重心と浮力の中心の位置によって決まります。重心が浮力の中心より下にある場合、物体は安定した平衡状態を保ちます。浮体の場合、安定性は浮力と物体の重量の相互作用から生じます。体が傾くと、浮力の中心が移動し、体を平衡状態に戻す復元偶力が発生します。ただし、背が高くて細い体の場合は、転倒偶力が発生し、不安定になり、転覆する可能性があります。

静止した物体が完全にまたは部分的に流体に沈むと、流体は浮力と呼ばれる力を物体に及ぼします。
この力は...

buoyancy-and-stability-for-submerged-and-floating-bodies

Education

JoVE Core

Civil Engineering

土木工学

Unit 1

ユニット1

Fluid Statics

流体静力学

KEY TERMS AND CONCEPTS

主要用語と概念

how buoyancy keeps bodies stable in water

Buoyancy and stability explain how submerged and floating bodies behave in a fluid. When a body is fully or partly under water and stays still, the fluid pushes upward on it. That upward push is called the buoyant force.

The buoyant force acts through the center of buoyancy. This is the center of the displaced fluid volume. Archimedes’ principle says the buoyant force equals the weight of the fluid displaced by the body.

Stability describes whether a body can return to its original position after it is moved. For submerged bodies, stability depends on the center of gravity and the center of buoyancy. If the center of gravity is below the center of buoyancy, the body stays in stable equilibrium.

Floating bodies become stable through the balance between buoyant force and weight. If the body tilts, the center of buoyancy shifts. That shift creates a restoring couple that turns the body back toward equilibrium. Tall, slender bodies may instead develop an overturning couple, which can make them unstable and lead to capsizing.

How Buoyancy Keeps Bodies Stable in Water

how-buoyancy-keeps-bodies-stable-in-water

concept of pressure at a point

Fluid Pressure at One Point

Fluid pressure at one point is the focus of this lesson. It shows that pressure in a fluid is the same in every direction at a single location. This happens because fluid molecules move randomly and collide with nearby molecules in a balanced way. At a given point, the pressure depends on the surrounding fluid molecules. It is affected by depth and density, not by the shape of the container or the way the fluid is oriented. In a fluid at rest, the pressure acts equally in all directions...

basic equation for pressure field

Pressure Balance in a Fluid Element

The pressure field equation describes how forces stay balanced inside a small fluid element. In fluid mechanics, this balance helps explain how pressure changes from one place to another within a fluid. Two main force types act on a fluid segment: surface forces and body forces. Surface forces come from pressure differences across nearby points in the fluid, so they depend on the local pressure gradient, which is the rate of pressure change with position. Body forces are spread through the...

pressure variation in a fluid at rest

Hydrostatic Pressure and Fluid Depth

Hydrostatic pressure describes how pressure changes with depth in a fluid at rest. In a stationary fluid, the fluid acceleration is zero, so the forces inside the fluid balance. That means pressure at a point below the surface depends on depth, not on the container’s shape or size. Only vertical forces affect the pressure change in this situation. These forces come from the weight of the fluid above a point. When pressure is compared at two different levels, the difference in pressure equals...

measurement of fluid pressure

Manometers and Gauges for Fluid Pressure

Fluid pressure is measured with manometers and related gauges. These tools use a liquid column to show pressure differences. The height of the column gives a simple reading of the force the fluid exerts. A basic manometer is the piezometer. It is a vertical tube that is open at the top and filled with the same fluid being measured. When the tube connects to a container, the fluid height in the tube matches the pressure inside that container. For more detailed measurements, the U-tube...

hydrostatic pressure force on a plane surface

hydrostatic-pressure-force-on-a-plane-surface

Hydrostatic Pressure on Submerged Surfaces

Hydrostatic pressure creates force on submerged plane surfaces. The force depends on the fluid pressure and the area of the surface. The way that force acts changes with the surface position. For a horizontal surface, the depth stays the same across the whole area. That means the pressure is uniform. The resultant force equals the pressure at that depth multiplied by the surface area, and it acts through the centroid of the surface. For a vertical surface, pressure increases as depth...

hydrostatic pressure force on a curved surface

hydrostatic-pressure-force-on-a-curved-surface

Finding the Force on Curved Fluid Surfaces

Hydrostatic pressure on curved surfaces is an important idea in fluid mechanics. It helps explain how water pushes on curved structures in civil engineering. Examples include reservoirs, dams, and storage tanks. The pressure changes in both size and direction along the curve. To find the total hydrostatic force on a curved surface, engineers isolate the fluid volume next to that surface. They then study the forces on imaginary horizontal and vertical planes that cut through the volume. The...

buoyancy and stability for submerged and floating bodies

Buoyancy and stability explain how submerged and floating bodies behave in a fluid. When a body is fully or partly under water and stays still, the fluid pushes upward on it. That upward push is called the buoyant force. The buoyant force acts through the center of buoyancy. This is the center of the displaced fluid volume. Archimedes’ principle says the buoyant force equals the weight of the fluid displaced by the body. Stability describes whether a body can return to its original position...

design example: application of archimedes' principle

design-example-application-of-archimedes-principle

Floating Block Buoyancy and Center of Buoyancy

Archimedes' principle is used to analyze the buoyant force on a wooden block that floats in seawater. The block has a rectangular section, and its dimensions, specific gravity, and the specific weight of seawater are used in the calculation. This setup shows how floating bodies stay in equilibrium. The first step is to find the weight of the block from its volume and specific gravity. Then Archimedes' principle is applied. The weight of the displaced water must equal the weight of the block.

key terms and concepts

Learn how buoyant force, the center of buoyancy, and Archimedes’ principle explain why submerged and floating bodies stay stable or capsize.

How Buoyancy Keeps Bodies Stable in Water | JoVE K12

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How Buoyancy Keeps Bodies Stable in Water

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