Name: free-body diagrams for force analysis
Uploaded: 2023-09-22T11:49:20.000Z
Duration: 1 min 28 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Physical Science

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

HS-PS2-3

Free-body Diagram

粒子に作用するすべての力を視覚的に表現したものは、フリーボディ図または力図と呼ばれます。複雑な問題を単純な表現に変換します。
フリーボディ図では、矢印の方向は力の方向を示し、矢印の長さは力の大きさを表します。
2つの段ボール箱が積み重ねられている固定台車を考えてみましょう。
ここで、関心のある2つのシステム、ボックス1とボックス2は、孤立したシステムであると仮定でき、単純なアウトラインまたはドットの形式の自由体図を使用して表すことができます。
ボックス1に作用する力は、その重量を定義する重力と、ボックス2による釣り合いの法線力です。
同様に、ボックス 2 にかかる力は、ボックス 2 の自重、トロリーによる垂直力、およびボックス 1 の重量です。
フリーボディ図は、特定の物理的状況から力学の抽象的な数学方程式への移行として、問題解決プロセスにおいて不可欠な役割を果たします。

<ol>
	<li>ヒベラー、RC(2016)。エンジニアリングメカニクス \u2012 静力学と力学。 ニュージャージー州ホーボーケン:ピアソンプレンティスホール。88ページ</li>
	<li>ビール、FP;ジョンストン、ER;マズレック、D.F;クロムウェル、PJおよびセルフ、BP(2019)。エンジニアのためのベクトル力学 \u2012 静力学と動力学。ニューヨーク:マグロウヒル。170-171ページ</li>
</ol>

自由体図

力学では、物体の運動を理解することが重要であり、この問題を解決するためのツールの1つが自由体図です。これは、物体に作用するすべての力を簡潔に表すためのシンプルでパワフルなグラフィカルな表現です。自由体図は、静止しているか動いている物体を表すことができ、物体の運動の原因を説明するために力学で使用されます。

自由体図は、複雑な問題をシンプルな表現に変換し、物体に作用する必要な力を理解しやすくし、数学的な方程式を導くのに役立ちます。多くの場合、自由体図を使用しないと非常に複雑な方程式を導くことができません。自由体図を作成するには、検査対象の物体またはシステムを選択し、その周囲から分離してドットまたはシンプルなアウトラインとして描きます。次に、物体または関心のあるシステムに作用するすべての必要な外力を矢印で表現します。矢印の方向は力の方向を表し、矢印の長さは力の大きさを示します。自由体図では、速度と加速度は表されませんが、物体に適用される力から推測することができます。

自由体図で表すことができる一般的な力には、重力、法線力、テンション、摩擦力、応用力などがあります。重力は物体に作用する重力の力であり、通常は下向きの矢印で表されます。法線力は、2つの物体が接触したときに発生する力であり、この力は物体の重力とは逆方向に作用します。テンションは、物体から離れた方向を指す矢印で一般的に表され、摩擦力は表面間の滑りを抵抗する力です。最後に、応用力は外部のエージェントによって物体に加えられる力を指し、押すまたは引くなどの方向を示す矢印で表されます。

静止している台車を考えてみましょう。その上に2つの段ボール箱が積まれています。興味のある2つのシステム、ボックス1とボックス2は孤立したシステムとしてみなすことができ、自由体図を使用して表すことができます。ボックス1に作用する力は、重力によって定義される重力の力と、ボックス2による相殺する法線力です。同様に、ボックス2に作用する力は、その重量、台車による法線力、およびボックス1の重量です。

力学では、物体の動きを理解することが不可欠であり、この問題を解決するのに役立つツールの1つがフリーボディ図です。シンプルだけど...

Education

JoVE Core

Mechanical Engineering

機械工学

Unit 1

ユニット1

Equilibrium of a Particle

粒子の平衡

KEY TERMS AND CONCEPTS

主要用語と概念

free-body diagrams for force analysis

Free-body diagrams help analyze the forces acting on an object in mechanics. They give a simple picture of a stationary or moving object and show why it moves the way it does. By turning a complex situation into a clear sketch, they make it easier to write the equation needed to solve the problem.

To draw a free-body diagram, first choose the object or system you want to study. Then isolate it from its surroundings and draw it as a dot or a simple outline. Add arrows for every important external force. The direction of each arrow shows the direction of the force, and the length shows its size.

A free-body diagram does not show velocity or acceleration. Those quantities are not drawn on the diagram, but they can be inferred from the forces acting on the object. Common forces include weight, normal force, tension, friction, and applied force. Weight is the force of gravity and is usually shown with an arrow pointing downward.

Normal force is the contact force between two objects touching each other. It acts in the direction opposite to the object's weight in many situations. Tension is usually drawn as an arrow away from the object and along the direction of the pull. Friction resists sliding between surfaces. Applied force is an outside push or pull, and it is shown with an arrow in the direction of that force.

A stationary trolley with two cardboard boxes stacked on it gives a clear example. Box one and box two can each be treated as separate isolated systems and shown with their own free-body diagrams. For box one, the forces are gravitational force and the balancing normal force from box two. For box two, the forces are its weight, the normal force from the trolley, and the weight of box one.

Free-Body Diagrams for Force Analysis

equilibrium conditions for a particle

Balanced Forces and Torque in Equilibrium

Equilibrium depends on balanced forces and balanced torque. An object in equilibrium is either at rest or moving with a constant velocity. These two cases are called static equilibrium and dynamic equilibrium. Static equilibrium means the object is not moving. Dynamic equilibrium means the object is moving, but its velocity stays constant. In both cases, the forces acting on the object must balance each other. Different forces can add, subtract, or cancel each other out. When the vector sum...

free-body diagram

Free-body diagrams help analyze the forces acting on an object in mechanics. They give a simple picture of a stationary or moving object and show why it moves the way it does. By turning a complex situation into a clear sketch, they make it easier to write the equation needed to solve the problem. To draw a free-body diagram, first choose the object or system you want to study. Then isolate it from its surroundings and draw it as a dot or a simple outline. Add arrows for every important...

steps for free-body diagram

Free-Body Diagram for Two-Block Motion

A free-body diagram helps analyze two-block motion in mechanics. It shows the forces acting on a system so the net force can be found and the acceleration can be calculated. The example in this lesson uses two blocks linked by a massless string over a frictionless pulley. Block 1 moves across a table while block 2 falls under gravity. The two blocks are treated as one isolated system. External forces are then identified and drawn as vector arrows on the diagram. For block 1, the forces...

free-body diagrams: problem solving

Free-Body Diagrams on Inclined Planes

Free-body diagrams help show the forces acting on an object on an inclined plane. A free-body diagram is a simple drawing that focuses only on the object or system being studied. It leaves out extra details so the force problem is easier to analyze and solve. For an example, a 10 kg block is released on a ramp that is 30° to the horizontal. The coefficient of friction is 0.2. The diagram for this block includes the weight from gravity, the normal force, and the frictional force. These are the...

coplanar forces

Resolving Coplanar Force Components

Coplanar forces act on an object in the same plane. To analyze this kind of system, each force is resolved into x and y components using Cartesian vector form and vector algebra. This makes it possible to test whether the object is in equilibrium. A coplanar system is in equilibrium when the resultant force is zero. That means the sum of the forces in each direction must also be zero. If the forces do not balance, the object is not in equilibrium and will accelerate in the direction of the net...

categories of equilibrium

Types of Equilibrium in Forces

Equilibrium in physics describes how forces act on a body so it stays still or moves at a constant speed. In two-dimensional force systems, equilibrium can be grouped into several categories based on how the forces are arranged. Collinear equilibrium is the simplest case. The forces act along one straight line, so only one force equation is needed in the direction of those forces. The other equations are already satisfied. Coplanar concurrent equilibrium is another category. In this case, all...

key terms and concepts

Learn how free-body diagrams show weight, normal force, tension, friction, and applied force. See how isolating an object simplifies force analysis in mechanics.

Free-Body Diagrams for Force Analysis | JoVE K12

JoVE Core 機械工学は、平衡、力、トラス解析、構造力学などの重要なトピックをカバーする簡潔でわかりやすいアニメーション ビデオを提供します。実際のアプリケーションを探索し、科学者主導の実験を通じてこれらのコンセプトが実際に動作しているのを目撃してください。

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HS-PS2-2

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HS-PS2-6

Free-Body Diagrams for Force Analysis

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