Contextualization

Theoretical Introduction

Elastic force is a fundamental concept in physics that describes the tendency of an elastomeric object (such as a spring, rubber band, or polymer) to return to its original shape after being deformed. British physicist Robert Hooke was the first to study elastic force in detail, and the law that bears his name (Hooke's Law) is the starting point for any discussion on this subject.

Hooke's Law states that the applied force is proportional to the deformation caused. In other words, the more you stretch or compress a spring, the greater the force it exerts to return to its original shape. This relationship is generally expressed as F = -kx, where F is the force, k is the elastic constant of the object, and x is the extension or compression of the object.

However, this law is only valid for certain limits of deformation, beyond which the object may not be able to return to its original shape or may even break. This limitation is called the elastic limit.

Contextualization

Elastic force has countless practical applications. The suspension of a car, for example, uses springs that absorb road irregularities, thanks to elastic force. The catapults of ancient castles used the force stored in a bow or other elastic structure to launch projectiles. Even in seemingly unrelated areas like medicine, elastic force is essential. For example, blood vessels are slightly elastic to better respond to blood pressure.

In this project, we will deepen our understanding of elastic force through a series of experiments and group discussions. Elastic force is a fundamental concept in physics, and by mastering it, you will be better prepared to understand a variety of phenomena, from the flight of an arrow to the expansion of the universe.

Practical Activity

Activity Title: Catapult Challenge

Project Objective

The main mission of the group will be to build a catapult using common materials and then carry out a series of experiments to explore elastic force and its practical applications. Additionally, they should write a detailed report explaining the concept of elastic force and how it was applied in the construction of the catapult.

Detailed Project Description

Each group of 3 to 5 students must design and build a catapult using low-cost materials such as popsicle sticks, rubber bands, adhesive tape, and plastic spoons. They will use elastic force to launch a small object, such as a cork or a paper ball, to a maximum distance.

During this process, students will need to research and understand which factors influence the distance the object will fly, such as the tension in the rubber band, the weight of the launched object, the launch angle, etc.

Once the catapults are ready, the groups will conduct a series of tests, recording different measurements and variables, such as the distance reached, the weight of the object, the launch angle, among others. Then, they will use this information to analyze the performance of their catapult and improve it.

Required Materials

• Popsicle sticks (50-100 units)
• Rubber bands (10-20 units)
• Adhesive tape
• Plastic spoon
• Small objects for launching (paper ball, cork, etc.)
• Ruler or measuring tape
• Scale (if available)
• Projector (for final presentation of the work)

Detailed Step-by-Step

1. Preliminary Research: Before starting the construction, students should research elastic force, the work of Robert Hooke, and how they are applied in the construction of catapults.

2. Catapult Design: After the research, students should sketch and plan their catapult, identifying where and how elastic force will be used.

3. Catapult Construction: With the design in hand, students should build the catapult using the suggested materials.

4. Tests and Experiments: Once the catapult is ready, students should conduct a series of tests, changing variables such as the weight of the object and the tension in the rubber band, and record the results.

5. Results Analysis: Students will use the collected data to identify patterns and relationships, discuss their results, and find ways to improve the design of their catapult.

6. Report Writing: Students should draw on what they have learned and their experiences during the project to write the report. It should include an introduction with the theory of elastic force, the development of the work with a detailed explanation of how the catapult was built and the tests performed, the tables and graphs prepared with the results obtained, and finally, the conclusions, discussing the results and what they learned. Do not forget to cite all references used in the bibliography!

7. Work Presentation: Each team will present their work to the class, explaining the design of their catapult, the tests they conducted, their results, and conclusions.

Each student is expected to dedicate at least 12 hours to this project, dividing the time between research, construction, experimentation, analysis, and report writing.

Project Deliverables

At the end of the project, each group must deliver:

1. The built catapult.
2. A written report with: Introduction (contextualizing the theme and its objective); Development (explaining the theory of elastic force, detailing the step-by-step construction of the catapult and the tests performed, as well as presenting the results obtained); Conclusions (concluding the work by summarizing its main points, explaining the learnings obtained, and the conclusions drawn about the project) and the Bibliography used.
3. An oral presentation of the project.

The technical and socio-emotional skills acquired will be evaluated throughout the process, from the construction of the catapult to the presentation of the work.