Notes, summaries, assignments, exams, and exercises for Technology for Secondary education

Understanding Forces and Mechanical Properties

A force is capable of producing action, changing the state of rest or motion of a body, or producing strains. The unit of force in the International System of Units (SI) is the newton (N).

Mechanical properties determine the behavior of materials when one or more forces are applied:

• Resistance: The ability of a material to withstand forces without excessive deformation or breakage (e.g., steel, wood, plastic).
• Toughness: The capacity to withstand repeated forces without breaking (e.g., metal, wood, some plastics). Its opposite is fragility (e.g., glass).
• Elasticity: The ability of a material to recover its original shape after being deformed (e.g., rubber).
• Plasticity: Materials that can be deformed

Common Characteristics of Machines

• Involve a kind of motion.
• Involve a kind of force.
• Make a job easier to do.
• Need some kind of input to make them work.
• Produce some kind of output.

Basic Types of Motion

• Rotary: Going round and round.
• Oscillating: Swinging backwards and forwards.
• Linear: In a straight line.
• Reciprocating: Backwards and forwards in a straight line.

A machine is a device that helps make work easier to perform.

Mechanical Advantage Defined

Mechanical Advantage: When a machine takes a small input force and increases the magnitude of the output force, a mechanical advantage has been produced.

Conservation of Energy Principle

Conservation of Energy: No machine can produce more work than the amount of work that is put into the machine.

The Six Simple

Fundamentals of Communication Systems

A communication system consists of a transmitter and a receiver that exchange information through a channel using coded messages (language). The communication channel is used to route messages from the sender to the receiver. Communication can be carried out through various means, including:

• Electronic Media: Radio, Television (TV), etc.
• Format: Written or Oral.

Transmission Media: Guided and Unguided

A means of transmission is defined as a physical support upon which one or more channels of transmission can carry data. These media are categorized as:

• Guided Media (Wired): Copper or cable transmission (e.g., Twisted Pair, Coaxial Cable).
• Unguided Media (Wireless): Air or vacuum, used in wireless communication.

The Concept of Invulnerability

The ability to avoid being harmed by external attacks is called invulnerability. While there are many myths, legends, and historical accounts regarding the search for such invulnerability, all these strategies have historically proven to have weaknesses.

Requirements for a Secure Computer System

Specific computer-level characteristics have been established that a truly invulnerable computer should fulfill:

• Be installed more than 20 feet underground.
• Remain disconnected from any other computer.
• Be isolated from the outside in a concrete structure.
• Possess an independent electrical system.

The Paradox of 100% Security

A 100% secure system is effectively 0% operational. Although it might be invulnerable to climatic disasters,...

Understanding Plastics

Plastics are corrosion-resistant, lightweight, and have low electrical conductivity. They possess good insulation properties but often have low tensile strength and are not suitable for use at high temperatures. While some are made with natural materials, most are obtained from petroleum and coal products. They derive their name from their ability to deform under pressure.

Thermoplastics

Thermoplastics soften when heated, can be molded into various forms, and harden again upon cooling. They are generally recyclable.

Polyethylene (Polythene)

Low-Density Polyethylene (LDPE)

• Weak, soft, and flexible.
• Softens at 85°C.
• Good insulation.
• Used for: bags, raincoats.

High-Density Polyethylene (HDPE)

• Rigid, strong, and resistant.
• Softens at

Hydraulic Flow Control Valves for Speed Regulation

Flow control valves are essential components used to regulate the speed of hydraulic actuators. There are three primary methods to implement these valves:

• Meter-In (Entry Regulation): The valve is placed between the pump and the actuator, controlling the fluid entering the system. Excess flow is diverted to the tank via the relief valve. This precise method is ideal for applications where the load consistently opposes actuator movement.
• Meter-Out (Output Regulation): This system is used when the load tends to run away from the actuator, moving in the same direction. The flow controller is installed to restrict the outlet flow from the actuator.
• Bleed-Off (Regulation by Subtraction): The valve is

Vehicle Wheel Functions and Nomenclature

Item 10: The wheel has the mission of supporting the vehicle, transmitting engine power, and ensuring that steering and brakes control the vehicle.

Understanding Tire Specifications

Nomenclature for controlling the wheels (e.g., 175 / 70 R13 82T tubeless):

• 175: Section of the tire in mm.
• 70: The percentage ratio between the tire height and section width.
• R: Radial casing.
• 13: Measurement between the seats (heels) in inches.
• 82: Load index (kg) according to the table.
• T: Maximum speed limit (homologation) according to the table.

Tire Performance and Wear Factors

Features of pneumatic tires:

• Kilometric performance: This refers to the mileage of the tires until their replacement. It is considered to have reached its

Pneumatic and Hydraulic Fluid Power Systems

Pneumatic and hydraulic fluids are used in machines for specific movements and efforts. Differences: Pneumatic systems use air as the fluid, while hydraulic systems use oil. To generate the air, a compressor is used, whereas a central hydraulic unit is required for hydraulics.

Applications of Fluid Power

Pneumatics: Used for alternative rectilinear and rotational movements of little strength, explosive environments, and tools.

Hydraulics: Used for alternative rectilinear and rotational movements of great strength and precise movements.

Pressure and Force Calculations

Force = Pressure x Area

The pressure can be measured in different units:

• 1 bar = 0.987 atm = 1 kp/cm² = 100,000 Pa = 760 mm Hg

Pneumatic Installation

Properties of Metals and Non-Metals

Non-Metals

• They have many electrons in the outer shell.
• Atoms want to be stable with the outer shell complete.
• Non-metals gain electrons.
• Non-metals do not let electrons flow (no electricity).

Metals

• They have many electrons in the outer shells.
• The atoms want to be stable with the outer shell complete.
• Metals lose electrons.
• Metals let electrons flow (electricity).

Components of an Electric Circuit

An electric circuit is the pathway for the flow of electrons. It consists of:

1. Generator: It is the element that provides the energy that electrons need to move. It obtains energy through technical processes.
2. Wire: It connects all the elements of a circuit. It is made of copper.
3. Loads or Receptors: They transform electrical energy

Brakes

Disc Brakes

A disc is connected to an axle. Brake pads apply pressure to the disc via friction.

Band Brakes

A drum is connected to an axle. A flexible band applies pressure to the outside of the drum.

Drum Brakes

A drum is connected to the axle. A pair of brake shoes apply pressure to the inside of the drum via friction.

Energy Absorption and Dissipation

Springs

Springs are devices that, thanks to the elasticity of their materials and their shape, can absorb energy when force is applied. This energy can then be dissipated in a controlled way. Depending on the type of external force applied, springs work in different ways:

• Compression: Pushing on the spring makes it shorter (e.g., a sofa).
• Traction: Pulling on the spring makes it longer (e.g., a