Introduction

• Relevance of the Theme: Simple and Thermal Machines are the basis of a multitude of innovations and technologies that we use daily. Unraveling their operation not only allows us to better understand the world around us but also gives us tools to design and optimize complex systems. From simple air conditioning to efficient hybrid cars, such machines are intimately present in our routine.

• Contextualization: It fits into the broader unit of 'Physics and its Applications.' The study of Simple and Thermal Machines bridges the gap between physical theory and its practical application, providing a conceptual basis that is essential for understanding more advanced concepts. In the 7th grade, it is the students' first immersion in Physics, making this topic essential from now on for understanding the world around us.

Theoretical Development

Components

• Definition of Simple Machines: They are devices that, due to their mechanical characteristics, allow the amplification of an applied force, a change of direction, or a variation in the intensity of a force.

  • Levers: Central concept. A rigid bar that can pivot around a fixed point (fulcrum). Classified into three types, depending on the relative position of the point of force application (power), the fulcrum, and the point of resistance. A deep understanding of levers is the key to mastering the concept of simple machines.

  • Pulleys: Consist of a wheel driven by a rope or chain, mounted with the purpose of changing the direction or intensity of a force. Classified as fixed, movable, and combined, depending on the number of rope or chain segments and how they are fixed.

  • Inclined Planes: Inclined flat surfaces that, when used to move objects, require less force than if the object were moved vertically. The principle of the inclined plane is widely applied in ramps and stairs.

  • Wedges and Screws: Both are seen as modulated forms of inclined planes that can change the direction or intensity of the applied force.

• Definition of Thermal Machines: They are devices that operate with heat and perform some type of work. The transformation of heat into work is based on the principle of energy conservation.

  • Thermal Engine: Class of thermal machine that converts thermal energy into mechanical work. It can be internal combustion, like car engines, or external combustion, like steam turbines.

  • Refrigerator and Heat Pumps: Inversion of the operation of a thermal machine. They absorb heat from a cold environment and transfer it to a hot environment. They are vital for air conditioning spaces and cooling equipment.

Key Terms

• Force: Action capable of modifying the state of motion or rest of an object.

• Work in Physics: Force applied to an object that causes a displacement in that object. Calculated as the product of force by distance.

• Thermal Energy: Form of energy associated with the temperature of a body or a system.

Examples and Cases

• Combustion Engine: Exemplifies the concept of a thermal machine. It transforms the energy contained in the fuel into mechanical energy through the combustion process.

• Rolling Kitchen Cart: Example of a simple machine that uses the lever principle.

• Mobile Delivery Truck: Uses the pulley principle in its crane to lift heavy loads.

• Staircase: The way we need to apply less force to climb stairs compared to a vertical wall illustrates the utility of inclined planes as simple machines.

• Screw: Facilitates the transfer of force from one direction to another, being able to lower or raise objects more easily.

Detailed Summary

Key Points

• Conceptualization of Simple Machines: Levers, pulleys, inclined planes, wedges, and screws are fundamental examples of simple machines that help us perform various types of work more efficiently and with less effort.
• Operating Principle of Levers: Levers, divided into three classes, are the paradigm of simple machines. They amplify or modify the direction of an applied force, depending on the relative position of the point of force application, the fulcrum, and the point of resistance.
• Practical Uses of Pulleys: Pulleys, depending on how they are mounted and moved, can be used to lift heavy loads, tie knots securely, and even reduce the effort needed to move objects.
• Deep Understanding of Inclined Planes: Understanding inclined planes is vital because they allow moving heavy objects with less effort, as seen in ramps and stairs.
• Wedges and Screws as Modifications of Inclined Planes: Wedges and screws are variants of the inclined plane and are used to split, raise, or fix objects, demonstrating the versatility and importance of this concept.

Conclusions

• Significant Relevance of Simple Machines: Virtually all modern technologies, from the simplest to the most complex, are based on the principles of simple machines.
• Principle of Energy Conservation in Thermal Machines: The work done by a thermal machine is derived from the waste of a useful part of heat, fulfilling the principle of energy conservation.
• Universal Applicability of Physical Concepts: A deep understanding of these physical concepts allows them to be applied in various everyday situations, becoming practical and indispensable tools.

Exercises

1. Explain, in your own words, what a lever is and cite an example of its use in everyday life.
2. Describe the difference between internal combustion and external combustion thermal machines.
3. Give two examples of simple machines that use the principle of the inclined plane and explain how they operate.