Name: work in force and motion
Uploaded: 2023-09-22T11:49:36.000Z
Duration: 1 min 14 s
Channel: JoVE

Work results when a force acting on an object displaces it. It is equal to the product of the scalar component of force along the displacement direction.
Mathematically, work can be given as the dot product of the applied force and the displacement of the object.
The SI unit of work is the joule. One joule is the work done when a one-newton force displaces an object by one meter.
Since work is a scalar quantity, its magnitude can be positive, negative or zero depending on the direction of the force relative to the displacement.

Consider the example of a crane lifting a load upward. Here, the applied force and displacement vectors are aligned in the same direction, so the work done is positive.

In another example, when brakes are applied to a moving car, the braking force acts in the opposite direction to the car&#39;s motion. Here, the work done is negative.

A frictionless pulley lifting a load through a massless inextensible string does zero work as force and displacement are perpendicular.

werk

Werk is een fundamenteel concept van werktuigbouwkunde en heeft vele toepassingen. Het begrijpen van hoe werk wordt berekend en de verschillende soorten werk kan ons helpen fysische processen beter te begrijpen en inzicht te krijgen in complexe problemen. Werk wordt gedefinieerd als het resultaat van een kracht die op een object werkt en ervoor zorgt dat het langs de lijn van de kracht beweegt. Het wordt ook gedefinieerd als het proces van energieoverdracht door middel van het toepassen van een kracht op een object, resulterend in de verplaatsing ervan. Deze energieoverdracht is verantwoordelijk voor de verandering in beweging of positie van het object. Werk kan worden geschreven als het product van de kracht en de component van de verplaatsing in dezelfde richting, of als het inproduct van de toegepaste kracht en verplaatsing van het object. Het SI-stelsel beschouwt één joule als zijn eenheid, dit komt overeen met het uitvoeren van één newton kracht over één meter verplaatsing. Het type werk dat op een object wordt verricht, is afhankelijk van de richting van de kracht ten opzichte van de verplaatsing. Als de toegepaste kracht en de verplaatsing parallel aan elkaar zijn, is het verrichte werk positief en als ze tegengesteld zijn, is het verrichte werk negatief. Wanneer de toegepaste kracht en de verplaatsing loodrecht op elkaar staan, is het verrichte werk nul. Een voorbeeld van positief verricht werk is wanneer een kraan een zware last optilt, door een opwaartse kracht uit te oefenen op de last, beweegt deze omhoog ten opzichte van het grondniveau. Negatief werk wordt verricht, bijvoorbeeld wanneer remmen worden toegepast op een bewegende auto, de wielen oefenen een kracht uit die tegen de beweging in gaat, resulterend in negatief verricht werk. Sommige krachten, zoals die op vaste punten of loodrecht op de verplaatsing, verrichten geen werk. Voorbeelden hiervan zijn de reactie op een wrijvingsloze pin wanneer het ondersteunde lichaam eromheen roteert, de reactiekracht op een lichaam dat over een wrijvingsloos oppervlak beweegt, enz. Krachten die wel werk verrichten, zijn onder meer het gewicht van een lichaam en de wrijvingskracht die op een lichaam werkt dat over een ruw oppervlak beweegt. In sommige gevallen is de som van het werk dat door meerdere krachten wordt verricht nul. Bijvoorbeeld, twee starre lichamen die verbonden zijn door een wrijvingsloze pin vereisen gelijke maar tegengestelde krachten voor beweging, waardoor hun gecombineerde werk nul is. Op dezelfde manier hebben twee blokken die verbonden zijn door een uittrekbare koord spankrachten van gelijke grootte maar tegengestelde tekens, wat resulteert in nul werk. Al met al kan begrip van welke krachten werk leveren en hoe werk kan worden berekend nuttige inzichten bieden in complexe fysische problemen en ons in staat stellen deze processen effectief te beheren voor de gewenste resultaten.

Werk

Work is a fundamental concept of mechanical engineering and has many applications. Understanding how work is calculated and the different types of work ...

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JoVE Core

Mechanical Engineering

Werktuigbouwkunde

Unit 1

Virtual Work

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KEY TERMS AND CONCEPTS

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Work

work in force and motion

Work connects force, motion, and energy in mechanics. It happens when a force acts on an object and the object moves along the line of action of that force. Work can also be described as energy transfer caused by applying a force, which leads to a change in the object’s motion or position.

Work is calculated as the force multiplied by the part of the displacement in the same direction as the force. It can also be written as the dot product of the applied force and the object’s displacement. In the SI system, the unit of work is the joule. One joule is equal to one newton of force acting over one meter of displacement.

The direction of the force compared with the displacement tells us the type of work done. When the force and displacement are parallel, the work is positive. When they are anti-parallel, the work is negative. When the force and displacement are perpendicular, the work is zero.

A crane lifting a heavy load is an example of positive work. The crane applies an upward force, and the load moves upward. Brakes on a moving car show negative work. The wheels exert a force that opposes motion, so work is done against the car’s movement.

Some forces do no work. This includes forces acting at fixed points or forces perpendicular to displacement. Examples include the reaction at a frictionless pin when a body rotates about it, and the reaction force on a body moving on a frictionless surface. Forces that do work include the weight of a body and friction acting on a body moving on a rough surface.

In some systems, the total work done by multiple forces is zero. Two rigid bodies connected by a frictionless pin need equal and opposite forces for motion, so their combined work is zero. The same idea applies to two blocks connected by an extensible cord, where the tension forces have equal magnitude but opposite signs. Knowing which forces produce work helps explain physical processes and solve mechanical problems.

Work in Force and Motion

work

Work connects force, motion, and energy in mechanics. It happens when a force acts on an object and the object moves along the line of action of that force. Work can also be described as energy transfer caused by applying a force, which leads to a change in the object’s motion or position. Work is calculated as the force multiplied by the part of the displacement in the same direction as the force. It can also be written as the dot product of the applied force and the object’s displacement. In...

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key terms and concepts

Learn how work is calculated from force and displacement, why it can be positive, negative, or zero, and see real examples from cranes and brakes.

Work in Force and Motion | 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.

mechanical engineering

Work in Force and Motion

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