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

Wizualna reprezentacja wszystkich sił działających na cząstkę nazywana jest diagramem swobodnego ciała lub diagramem siły. Przekształca złożone problemy w proste reprezentacje.
Na diagramie swobodnego ciała kierunek strzałek wskazuje kierunek sił, podczas gdy długość strzałek reprezentuje wielkość sił.
Weźmy pod uwagę wózek stacjonarny, na którym ułożone są dwa kartony.
W tym przypadku można założyć, że dwa interesujące nas systemy, ramka pierwsza i ramka druga, są układami izolowanymi i mogą być reprezentowane za pomocą diagramu swobodnego ciała w postaci prostego konturu lub kropki.
Siły działające na pudełko pierwsze to siła grawitacji, która określa jego wagę, oraz przeciwrównoważąca siła normalna spowodowana pudełkiem drugim.
Podobnie, siły działające na pudło drugie to jego ciężar własny, siła normalna działająca na wózek i waga pudełka pierwszego.
Diagramy ciał swobodnych odgrywają integralną rolę w procesie rozwiązywania problemów jako przejście od określonej sytuacji fizycznej do abstrakcyjnego równania matematycznego w mechanice.

<ol>
	<li>Hibbeler, R.C. (2016). Mechanika inżynierska \u2012 Statyka i dynamika. Hoboken, New Jersey: Pearson Prentice Hall. Strona 88</li>
	<li>Piwo, F.P.; Johnston, E.R.; Mazurek, D.F.; Cromwell, PJ i Self, BP (2019). Mechanika wektorowa dla inżynierów \u2012 Statyka i dynamika. Nowy Jork: McGraw-Hill. Strony 170-171</li>
</ol>

diagram sił swobodnych

W mechanice zrozumienie ruchu obiektów jest kluczowe, a jednym z narzędzi, które pomagają rozwiązać ten problem, jest diagram sił swobodnych. Jest to prosty, ale potężny sposób graficznej reprezentacji, który zwięźle ukazuje wszystkie siły działające na obiekt. Diagram sił swobodnych może przedstawiać obiekt nieruchomy lub poruszający się i jest używany w mechanice do wyjaśnienia przyczyny ruchu obiektu.

Diagram sił swobodnych przekształca złożony problem w prostą reprezentację, ułatwiającą zrozumienie istotnych sił działających na obiekt, prowadzących do równania matematycznego. W wielu przypadkach równanie to byłoby bardzo trudne do otrzymania bez użycia diagramów sił swobodnych. Aby stworzyć diagram sił swobodnych, zacznij od wybrania obiektu lub systemu poddanego badaniu, odizoluj go od otoczenia i przedstaw go jako kropkę lub prosty zarys. Następnie przedstaw wszystkie istotne siły zewnętrzne działające na obiekt lub system zainteresowania za pomocą strzałek. Kierunek strzałek reprezentuje kierunek siły, a długość strzałek przedstawia wartość siły. Ważne jest, aby zauważyć, że w diagramie sił swobodnych prędkość i przyspieszenie nie są reprezentowane, ale można je wywnioskować na podstawie sił działających na obiekt.

Niektóre powszechne rodzaje sił, które można przedstawić na diagramie sił swobodnych, to waga, siła normalna, napięcie, tarcie i siła zewnętrzna. Waga odnosi się do siły grawitacji działającej na obiekt, zwykle przedstawianej jako strzałka skierowana w dół. Siła normalna to siła między dwoma obiektami, gdy są one w kontakcie; działa ona w przeciwnym kierunku do wagi obiektu. Napięcie jest ogólnie przedstawiane jako strzałka skierowana od obiektu w kierunku siły, a tarcie to siła oporu przesuwania się między powierzchniami. Na koniec, siła zewnętrzna odnosi się do siły wywieranej na obiekt przez zewnętrznego agenta, takiego jak popychanie lub ciągnięcie. Siły zewnętrzne są przedstawiane strzałką skierowaną w kierunku siły.

Rozważmy nieruchomą wózkę, na której są umieszczone dwie kartonowe skrzynki. Dwa systemy zainteresowania, skrzynka pierwsza i skrzynka druga, można traktować jako izolowane systemy i przedstawić za pomocą diagramu sił swobodnych. Siły działające na skrzynkę pierwszą to siła grawitacyjna, która określa jej wagę, oraz równoważąca ją siła normalna związana z drugą skrzynką. Podobnie, siły działające na skrzynkę drugą to jej waga, siła normalna od wózka i waga skrzynki pierwszej.

Diagram sił swobodnych

W mechanice zrozumienie ruchu obiektów jest niezbędne, a jednym z narzędzi, które pomaga rozwiązać ten problem, jest diagram swobodnego ciała. Jest to proste, ale ...

Education

JoVE Core

Mechanical Engineering

Inżynieria mechaniczna

Unit 1

Jednostka 1

Equilibrium of a Particle

Równowaga punktu materialnego

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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 Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

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HS-PS2-6

Free-Body Diagrams for Force Analysis

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