Name: free-body diagram for two-block motion
Uploaded: 2025-05-22T09:06:02.000Z
Duration: 1 min 22 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

Steps for Free-Body Diagram

Si consideri un sistema di due blocchi accoppiati da una corda senza massa su una puleggia. Il blocco 1 scivola su una tavola tirata dal blocco 2 mentre cade sotto la gravità. 
L'accelerazione del sistema può essere derivata calcolando la forza netta sul sistema.
Un diagramma di corpo libero per questo sistema può essere disegnato rappresentando i due blocchi con il loro contorno. In questo caso, i blocchi sono considerati isolati.
Le forze esterne che agiscono su di esse sono identificate e rappresentate da frecce vettoriali.
Le forze sul blocco 1 sono il suo peso, la forza normale, la forza di tensione dovuta alla fune e la forza di attrito che si oppone alla forza di tensione che causa il movimento.
Allo stesso modo, le forze che agiscono sul blocco 2 sono il suo peso e la forza di tensione.
Applicando la seconda legge del moto di Newton ai blocchi, si può derivare un'equazione per la forza netta.
Utilizzando l'operazione algebrica e riorganizzando i termini, è possibile ottenere l'entità dell'accelerazione del sistema.

<ol>
	<li>Hibbeler, R.C. (2016). Ingegneria Meccanica \u2012 Statica e Dinamica. Hoboken, New Jersey: Pearson Prentice Hall. pagine 89</li>
	<li>Birra, F.P.; Johnston, E.R.; Mazurek, D.F; Cromwell, P.J. e Self, B.P. (2019). Meccanica vettoriale per ingegneri \u2012 Statica e dinamica. New York: McGraw-Hill. pagine 171-172</li>
</ol>

passaggi per il diagramma di corpo libero

Quando si tratta di studiare il comportamento degli oggetti nella meccanica, uno degli strumenti più importanti a disposizione è il diagramma di corpo libero. Prendiamo in considerazione un semplice esempio di un sistema composto da due blocchi accoppiati da un filo privo di massa sopra una carrucola priva di attrito. Il blocco 1 sta scivolando su un tavolo tirato dal blocco 2 mentre il blocco 2 cade a causa della gravità.

Per trovare l'accelerazione del sistema, è prima necessario calcolare la forza netta sul sistema. Per fare ciò, è possibile creare un diagramma di corpo libero per rappresentare i due blocchi, che vengono considerati come un singolo sistema isolato dall'ambiente circostante. Le forze esterne vengono quindi identificate e rappresentate nel diagramma da frecce vettoriali.

Quando si osserva il blocco 1, varie forze agiscono su di esso. Queste includono il suo peso, la forza normale, la forza di tensione dovuta al filo e la forza di attrito che si oppone alla forza di tensione, causando così il movimento. Per il blocco 2, il suo peso e le forze di tensione sono le uniche forze che agiscono su di esso.

Una volta creato il diagramma del corpo libero, è possibile applicare la seconda legge del moto di Newton ai blocchi. Facendo ciò, è possibile derivare un'equazione per la forza netta che agisce sul sistema. Questa equazione includerà le masse dei blocchi, l'accelerazione del sistema e le forze che agiscono su ciascun blocco.

Con l'equazione in mano, è poi possibile utilizzare operazioni algebriche per riorganizzare i termini e risolvere la magnitudine dell'accelerazione del sistema. Il risultato sarà un valore numerico che rappresenta come il sistema si comporterà sotto le forze date.

L'importanza di un diagramma di corpo libero in questa situazione non può essere sottovalutata. Fornisce una rappresentazione chiara e concisa delle forze in gioco, consentendo quindi un calcolo dell'accelerazione del sistema più facile e accurato. Senza questo strumento, sarebbe molto più difficile comprendere e analizzare il comportamento dei blocchi e delle forze che agiscono su di essi.

Passaggi per il diagramma di corpo libero

Quando si tratta di studiare il comportamento degli oggetti in meccanica, uno degli strumenti più importanti a disposizione è il diagramma di corpo libero. Considera un semplice ...

Education

Didattica

JoVE Core

Mechanical Engineering

Ingegneria Meccanica

Unit 1

Unità 1

Equilibrium of a Particle

Equilibrio di una particella

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 include weight, the normal force, tension from the rope, and friction that opposes the tension force. For block 2, the forces are its weight and the tension force.

After the free-body diagram is complete, Newton’s second law of motion can be applied to the blocks. This gives an equation for the net force on the system. The equation includes the masses of the blocks, the acceleration of the system, and the forces acting on each block.

With the equation set up, algebra can be used to rearrange the terms and solve for the magnitude of the acceleration. The result is a numerical value that describes how the system will move under the given forces. The diagram makes the force analysis clearer and more accurate.

Free-Body Diagram for Two-Block Motion

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 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...

steps for free-body diagram

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

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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

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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 a free-body diagram is used to analyze two blocks connected by a string and pulley, identify forces, and solve for acceleration.

Free-Body Diagram for Two-Block Motion | JoVE K12

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HS-PS2-6

Free-Body Diagram for Two-Block Motion

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