Objectives (5 - 7 minutes)

1. Understand the concept of work and its relationship with the elastic force, in order to be able to apply this theory to practical problems.
2. Develop skills to calculate the work done by an elastic force using the formula W = 1/2 k x², where W is the work, k is the elastic constant, and x is the elastic deformation.
3. Apply the learned theory to solve practical problems involving elastic force and work, providing students with an opportunity to consolidate their knowledge and skills.

Secondary Objectives

• Stimulate critical thinking and problem-solving, encouraging students to apply theoretical knowledge in practical situations.
• Promote interaction among students, encouraging discussion and exchange of ideas during practical activities.
• Develop research and autonomous study skills, as inverted classroom requires students to study the material beforehand.

Introduction (10 - 15 minutes)

1. Review of Previous Concepts: The teacher starts the lesson by reviewing the concepts of work and elastic potential energy, which were previously studied. Questions will be asked to the students to verify their retention of these concepts, thus ensuring a solid foundation for the new content to be covered. (3 - 4 minutes)
2. Problem Situation 1: The teacher proposes the following problem situation: 'Imagine you are playing with a slingshot. By stretching the slingshot's rubber, you are applying a force that generates an elastic deformation. When you release the slingshot, it propels an object. How can we calculate the work done by the slingshot's elastic force in this case?' (3 - 4 minutes)
3. Problem Situation 2: The teacher proposes another problem situation: 'Let's suppose we have a hair elastic. By stretching it, we observe that the more we stretch it, the harder it becomes to stretch even further. Why does this happen and how can we calculate the elastic force we are applying?' (3 - 4 minutes)
4. Contextualization: The teacher explains that elastic force is a physical concept present in various everyday situations, such as when using rubber bands, springs, and slingshots. Furthermore, understanding this concept is essential in various fields, such as engineering, architecture, and design. (2 - 3 minutes)
5. Capturing Students' Attention: To spark students' interest, the teacher can share some curiosities, such as the fact that elastic force is used to measure the stiffness of materials in scientific experiments or that elastic force is the force responsible for the operation of many toys and equipment, such as toy cars and trampolines. Additionally, the teacher can show images or videos of real examples of elastic force in action, such as the slingshot being used to launch a projectile. (2 - 3 minutes)

Development (20 - 25 minutes)

1. Theory Presentation (10 - 12 minutes)

   1.1. Elastic Force (3 - 4 minutes): The teacher begins the theoretical presentation by explaining that elastic force is the force that an elastic object, such as a spring or a slingshot, exerts when stretched or compressed. This force is directly proportional to the deformation of the elastic object, meaning that the more the object is stretched or compressed, the greater the elastic force it exerts.

   1.2. Work (3 - 4 minutes): Next, the teacher explains the concept of work in physics, which is the energy transferred to an object when a force acts on it, causing a displacement. Work is calculated by multiplying the force by the displacement in the direction of the force.

   1.3. Relationship between Elastic Force and Work (3 - 4 minutes): The teacher then connects the concepts of elastic force and work, explaining that the work done by an elastic force can be calculated using the formula W = 1/2 k x², where W is the work, k is the elastic constant of the object, and x is the elastic deformation.

2. Problem Solving (8 - 10 minutes)

   2.1. Problem 1 - Work done by a slingshot (4 - 5 minutes): The teacher proposes the first problem, which is to calculate the work done by a slingshot when propelling an object. Students should use the formula W = 1/2 k x², where k is the elastic constant of the slingshot and x is the elastic deformation. The teacher guides the students to identify the necessary information in the problem statement and substitute it into the formula to find the answer.

   2.2. Problem 2 - Elastic force of a hair elastic (4 - 5 minutes): The teacher proposes the second problem, which is to calculate the elastic force of a hair elastic given a certain elongation. Students should use the formula for elastic force, F = k x, where F is the elastic force, k is the elastic constant of the elastic, and x is the elongation. The teacher guides the students to identify the necessary information in the problem statement and substitute it into the formula to find the answer.

3. Discussion and Clarification of Doubts (2 - 3 minutes): The teacher concludes the Development stage by promoting a discussion on the solutions to the proposed problems. Students are encouraged to share their solutions and clarify any doubts they may have. The teacher takes this opportunity to reinforce the discussed concepts and correct any misconceptions that may have occurred.

Return (8 - 10 minutes)

1. Connection with the Real World (3 - 4 minutes): The teacher should encourage students to make the connection between what was learned in the lesson and the real world. To do this, the following topics can be discussed:

   1.1. Practical Applications: The teacher can ask students about other everyday situations where elastic force is present, in addition to those already discussed. For example, the operation of a trampoline, the suspension of a car, the pressure of a bow and arrow, among others. This discussion not only reinforces the learned concept but also allows students to realize the relevance of physics in the world around them.

   1.2. Relevance of the Formula: The teacher can also revisit the formula for the work done by the elastic force (W = 1/2 k x²) and question the students about its importance. The teacher can explain that this formula not only allows for the calculation of work but also provides information about the elasticity of the object, indicating, for example, that the higher the elastic constant (k), the greater the work done.

2. Reflection on Learning (2 - 3 minutes): The teacher asks students to reflect individually on what they learned in the lesson. To assist them in this process, the teacher can propose the following questions:

   2.1. Most Important Moment: What was the most important concept learned today? Why?

   2.2. Remaining Doubts: What doubts have not been clarified yet? What would you like to learn more about on the subject?

3. Sharing Reflections (2 - 3 minutes): Next, students are invited to share their reflections with the class. This activity not only allows students to consolidate their learning but also promotes interaction among them, encouraging the exchange of ideas and respect for others' opinions.

4. Teacher's Feedback (1 minute): Finally, the teacher provides general feedback on the lesson, highlighting strengths and pointing out areas that still need more attention. The teacher also reinforces the importance of the subject, encouraging students to continue studying and practicing the concepts learned.

Conclusion (5 - 7 minutes)

1. Content Summary (2 - 3 minutes): The teacher recaps the main points covered during the lesson. This includes the concept of work, the definition and importance of elastic force, and the formula to calculate the work done by an elastic force (W = 1/2 k x²). The teacher also recalls the practical problems that were solved and how they helped illustrate the application of theoretical concepts.

2. Connection between Theory, Practice, and Applications (1 - 2 minutes): The teacher emphasizes how the lesson connected theory, practice, and applications. He reiterates that the theoretical understanding of the concept of elastic force and work is crucial for solving practical problems, and that these skills are valuable in various real-world applications, from designing structures to operating everyday devices.

3. Extra Materials (1 minute): The teacher suggests additional materials for students who wish to deepen their understanding of the subject. These resources may include physics books, educational videos online, interactive physics simulators, and question-and-answer websites. For example, the teacher can suggest a simple experiment that students can perform at home to observe elastic force in action.

4. Relevance of the Subject (1 - 2 minutes): Finally, the teacher highlights the importance of the subject in everyday life. He reiterates that elastic force is a fundamental concept in many areas of science and engineering, and that understanding how to calculate the work done by an elastic force can be useful in various practical situations. The teacher may, for example, mention how understanding elastic force is crucial for developing new materials and technologies, such as creating more efficient springs or optimizing the design of structures that need to absorb impacts.