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

חשבו על מערכת של שני בלוקים המחוברים על ידי חוט חסר מסה מעל גלגלת. בלוק 1 מחליק על שולחן שנמשך על ידי בלוק 2 כשהוא נופל תחת כוח הכבידה. 
ניתן לגזור את תאוצת המערכת על ידי חישוב הכוח נטו על המערכת.
ניתן לשרטט דיאגרמת גוף חופשי עבור מערכת זו על ידי ייצוג שני הבלוקים עם קווי המתאר שלהם. כאן, הבלוקים נחשבים מבודדים.
הכוחות החיצוניים הפועלים עליהם מזוהים ומיוצגים על ידי חצים וקטוריים.
הכוחות בבלוק 1 הם משקלו, הכוח הנורמלי, כוח המתח הנובע מהחבל וכוח החיכוך המנוגד לכוח המתח הגורם לתנועה.
באופן דומה, הכוחות הפועלים על בלוק 2 הם משקלו וכוח המתח.
אם מיישמים את חוק התנועה השני של ניוטון על הבלוקים, ניתן לגזור משוואה עבור הכוח נטו.
באמצעות הפעולה האלגברית וסידור מחדש של המונחים, ניתן לקבל את גודל התאוצה של המערכת.

<ol>
	<li>היבלר, R.C. (2016). מכניקה הנדסית - סטטיקה ודינמיקה. הובוקן, ניו ג'רזי: אולם פירסון פרנטיס. עמ' 89</li>
	<li>באר, פ"פ; ג'ונסטון, א.ר.; מזורק, ד"ו; קרומוול, פי ג'יי ועצמי, ב. (2019). מכניקה וקטורית למהנדסים - סטטיקה ודינמיקה. ניו יורק: מקגרו-היל. עמ' 171-172</li>
</ol>

שלבים עבור דיאגרמת גוף חופשי

<div style="direction:rtl">כשזה מגיע לחקר התנהגותם של עצמים במכניקה, אחד הכלים החשובים ביותר שקיימים הוא דיאגרמת הגוף החופשי. חשבו על דוגמה פשוטה של מערכת של שני בלוקים מחוברים על ידי מיתר חסר מסה על גלגלת ללא חיכוך. בלוק 1 מחליק מעל שולחן שנמשך על ידי בלוק 2 כאשר בלוק 2 נופל תחת כוח הכבידה. כדי למצוא את תאוצת המערכת, תחילה יש צורך לחשב את הכוח הנקי על המערכת. על מנת להשיג זאת, ניתן ליצור דיאגרמת גוף חופשי המייצגת את שני הבלוקים, הנחשבת כמערכת בודדת המבודדת מהסביבה. לאחר מכן מזוהים הכוחות החיצוניים ומיוצגים על ידי חיצים וקטוריים בתרשים. כאשר מסתכלים על בלוק 1, מספר כוחות פועלים עליו. אלה כוללים את משקלו, הכוח הרגיל, כוח המתח הנובע מהחבל וכוח החיכוך שמתנגד לכוח המתיחה, ובכך גורם לתנועה. עבור בלוק 2, משקלו וכוחות המתח הם הכוחות היחידים הפועלים עליו. לאחר יצירת דיאגרמת הגוף החופשי, ניתן ליישם את חוק התנועה השני של ניוטון על הבלוקים. על ידי כך, ניתן לגזור משוואה עבור הכוח הנקי הפועל על המערכת. משוואה זו תכלול את מסות הבלוקים, תאוצת המערכת והכוחות הפועלים על כל גוש. כאשר המשוואה ביד, אפשר להשתמש בפעולות אלגבריות כדי לסדר מחדש את המונחים ולפתור את גודל התאוצה של המערכת. התוצאה תהיה ערך מספרי המייצג את האופן שבו המערכת תתנהג תחת הכוחות הנתונים. אי אפשר להפריז בחשיבותו של דיאגרמת גוף חופשי במצב זה. היא מספקת ייצוג ברור ותמציתי של הכוחות הפועלים, ובכך מאפשרת חישוב קל ומדויק יותר של תאוצת המערכת. ללא כלי זה, יהיה הרבה יותר קשה להבין ולנתח את התנהגות הבלוקים והכוחות הפועלים עליהם.</div>

כשמדובר בחקר ההתנהגות של אובייקטים במכניקה, אחד הכלים החשובים ביותר הזמינים הוא דיאגרמת הגוף החופשי. שקול פשוט ...

Education

JoVE Core

Mechanical Engineering

הנדסת מכונות

Unit 1

יחידה 1

Equilibrium of a Particle

שיווי משקל של חלקיק

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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

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 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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Free-Body Diagram for Two-Block Motion

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