Positive and negative work |⚡3d animation | Class 9, Physics |

The Visual Mastering
17 Sept 202204:17
EducationalLearning
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TLDRThis educational module explores the concept of positive and negative work in physics. It explains that work is positive when force and displacement are in the same direction, such as pushing a table or pulling a toy cart on a smooth floor. Conversely, negative work occurs when the force opposes the displacement, as demonstrated by friction acting against a moving carton box. The module clarifies that the total work is the sum of positive and negative work, illustrating this with the net force and displacement of the box, emphasizing the importance of directionality in determining the type of work done.

Takeaways
  • 😀 Work can be both positive and negative, depending on the direction of the force relative to the displacement.
  • 🚀 In the case of force and displacement being in the same direction, such as a boy pushing a table or a child pulling a toy cart, the work done is positive.
  • 🔧 When a force is applied and the body moves in the direction of the force, the work done by that force is considered positive.
  • 🛠️ Frictional force acts in the opposite direction of the displacement and does negative work, as it opposes the motion.
  • 📦 Pushing a carton box on a rough surface involves positive work by the person's force and negative work by the frictional force.
  • ➕ The total or net work done on an object is the sum of the positive and negative work acting on it.
  • 🔄 The work done by the force is calculated as the product of the force (F) and the displacement (s), with a negative sign for forces acting in the opposite direction.
  • 📈 The net force on an object can be found by subtracting the frictional force from the applied force, and the net work is the product of this net force and the displacement.
  • 🔄 The negative sign in the work calculation for friction implies that it acts in the opposite direction to the applied force.
  • 📚 Understanding the direction of forces and their effects on work is crucial for analyzing mechanical systems.
  • 🔑 The concept of net work is important for determining the overall effect of multiple forces acting on an object.
Q & A

  • What is the concept of positive and negative work in physics?

    -Positive and negative work in physics refer to the work done by a force on a body based on the direction of the force relative to the direction of displacement. Positive work occurs when the force and displacement are in the same direction, while negative work occurs when they are in opposite directions.

  • In the script, what are the two situations described where force and displacement are in the same direction?

    -The two situations are: 1) A boy shifts a table from one spot to another in a room by pushing it over the smooth floor, and 2) A small child pulls a toy cart over a smooth floor. In both cases, the force applied and the direction of displacement are the same, resulting in positive work.

  • What is the difference between the work done by the applied force and the frictional force when pushing a carton box on a rough surface?

    -The applied force does positive work because its direction is the same as the displacement of the carton box. In contrast, the frictional force does negative work because its direction is opposite to the displacement of the carton box.

  • How is the work done by a force on a body defined when the force is in the opposite direction of the body's displacement?

    -When a force acts on a body in a direction opposite to that of the body's displacement, the work done by the force on the body is considered negative.

  • What is the formula for calculating the work done by a force when the force and displacement are in opposite directions?

    -The work done by the force in such a case is calculated as the product of the force (F) and the negative of the displacement (-s), or mathematically, as -F * s.

  • In the context of the script, what does the negative sign for frictional force imply?

    -The negative sign for frictional force implies that it is acting in the direction opposite to that of the applied force, thus doing negative work on the body.

  • How is the total or net work done on the cotton box calculated in the script?

    -The total or net work done on the cotton box is the sum of the positive work done by the applied force and the negative work done by the frictional force, which is calculated as the applied force (F) minus the frictional force (f), all multiplied by the displacement (s).

  • What is the relationship between the applied force, frictional force, and the net force on the cotton box?

    -The net force on the cotton box is the difference between the applied force (F) and the frictional force (f). If the applied force is greater than the frictional force, the net force is positive, resulting in the cotton box moving in the direction of the applied force.

  • How can the total work done on the cotton box also be calculated by considering the net force and its displacement?

    -The total work done on the cotton box can also be calculated by multiplying the net force acting on the box by its displacement. This method yields the same result as summing the positive and negative work.

  • What is the significance of understanding positive and negative work in analyzing physical situations?

    -Understanding positive and negative work is crucial for accurately analyzing and calculating the total work done on a body in various physical situations, especially when multiple forces are acting in different directions.

  • Can the concept of positive and negative work be applied to non-physical scenarios?

    -While the concept of positive and negative work is specific to physics, the underlying idea of forces working in harmony or opposition can be metaphorically applied to non-physical scenarios, such as teamwork or conflicting interests.

Outlines
00:00
🔄 Understanding Positive and Negative Work

In this module, you will explore the concepts of positive and negative work. Work can be either positive or negative depending on the direction of the force and displacement. For instance, when a boy pushes a table or a child pulls a toy cart over a smooth floor, the force and displacement are in the same direction, resulting in positive work. Conversely, when a person pushes a carton box on a rough surface, the frictional force opposes the motion, resulting in negative work. The total work done on an object is the sum of positive and negative work, which can also be calculated using the net force and displacement. This module concludes by explaining that the net work done is the product of the net force and the displacement of the object.

Mindmap
Keywords
💡Work
Work in physics is defined as the product of the force applied to an object and the displacement of the object in the direction of the force. It is a scalar quantity and can be positive or negative, depending on the direction of the force relative to the displacement. In the script, work is discussed in the context of moving objects like a table and a toy cart, illustrating the concept with examples of positive work when the force and displacement are in the same direction.
💡Positive Work
Positive work occurs when the force applied to an object and the displacement of the object are in the same direction. This means that the force is aiding the motion of the object. In the video, positive work is exemplified by a boy pushing a table and a child pulling a toy cart on a smooth floor, where the applied force and the direction of movement are aligned.
💡Negative Work
Negative work is done when the force applied opposes the direction of the object's displacement. This typically happens with forces like friction, which resist motion. The script explains negative work through the example of a person pushing a carton box on a rough surface, where the frictional force does negative work because it acts in the opposite direction to the box's displacement.
💡Force
Force is any interaction that, when unopposed, will change the motion of an object. It can cause an object with mass to change its velocity, which includes to begin moving from a state of rest, or to stop moving. In the script, force is essential in doing work, as seen in the examples of pushing and pulling objects, where the force applied results in work being done.
💡Displacement
Displacement is the change in position of an object. It is a vector quantity, meaning it has both magnitude and direction. In the context of the video, displacement is crucial for determining whether work is positive or negative, as it is the movement of the object in response to the applied force.
💡Frictional Force
Frictional force is the resistance that one surface or object encounters when moving over another. It is a type of force that opposes the relative motion or tendency of such motion. In the script, frictional force is highlighted as doing negative work when it acts in the opposite direction to the displacement of the carton box.
💡Smooth Floor
A smooth floor in the context of the video represents an ideal surface with minimal friction, allowing for easier movement of objects. The script uses the smooth floor as a condition in the examples where positive work is done without the interference of friction.
💡Rough Surface
A rough surface, as mentioned in the script, is the opposite of a smooth floor, characterized by a higher frictional force that opposes the motion of objects. The rough surface is used to demonstrate how friction does negative work when a person pushes a carton box.
💡Net Force
Net force is the vector sum of all the forces acting on an object. It is the force that actually causes the object to accelerate according to Newton's second law of motion. In the script, the net force is calculated by subtracting the frictional force from the applied force, which results in the force that effectively does work on the cotton box.
💡Net Work
Net work, as discussed in the script, is the total work done on an object when considering all forces acting on it. It is the sum of the positive and negative work, and in the case of the cotton box, it is the work done by the net force, which is the applied force minus the frictional force.
💡Carton Box
The carton box in the script serves as a practical example to illustrate the concepts of work, positive work, and negative work. It is used to demonstrate how work is done when the box is pushed on both smooth and rough surfaces, highlighting the role of friction in doing negative work.
Highlights

Work can be positive or negative depending on the direction of force and displacement.

Positive work occurs when force and displacement are in the same direction.

Examples of positive work include a boy pushing a table and a child pulling a toy cart on a smooth floor.

Negative work is done when the force acts in the opposite direction of the body's displacement.

Frictional force does negative work as it opposes the motion of an object.

The formula for work done by a force is the product of force and displacement (W = F * s).

Negative work is represented by the product of the negative force and displacement (W = -F * s).

Frictional force is considered negative as it acts in the opposite direction to the applied force.

Total work done on an object is the sum of positive and negative work.

Total work can also be calculated using the net force and displacement of the object.

The applied force is usually greater than the frictional force, resulting in a net positive force.

The net force on an object determines the total work done on it.

Understanding the concepts of positive and negative work is crucial for analyzing mechanical systems.

Work done by friction is an essential factor in determining the total work on an object.

The direction of force and displacement is key to determining whether work is positive or negative.

The module concludes with the understanding that the sum of positive and negative work gives the total work done on an object.

Transcripts

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Related Tags
Positive WorkNegative WorkPhysics ConceptsForce DisplacementFrictional ForceMechanical WorkApplied ForceCotton BoxSmooth FloorNet ForceWork Calculation