Lesson Notes By Weeks and Term v5 - Grade 9

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Identify and explain types of structures.
• Analyze technological systems (input, process, output).
• Explain the functions of electronic components.
• Identify different types of motion in mechanisms.
• Understand open and closed loop control systems.

Lesson summary

This week is dedicated to revision and exam preparation for our Grade 9 Technology curriculum. This is crucial as it consolidates all the knowledge and skills you've acquired throughout the term, preparing you for the upcoming assessments. Understanding technology and its applications is vital in South Africa, allowing you to contribute to innovation, problem-solving, and economic growth within our communities. From using technology to improve agricultural practices in rural areas to developing sustainable energy solutions, your technological skills will be essential for building a better future for our country.

Lesson notes

2.1 Structures A structure is any arrangement of materials that can support a load. Structures are categorized into three main types: Solid Structures: These are made from a single piece of material or multiple pieces rigidly joined together. Examples include a brick wall, a dam wall, or a wooden table. In the South African context, think of traditional mud houses or concrete bus shelters. Solid structures rely on their own weight and the strength of the material to resist forces.

Frame Structures: These consist of individual members joined together to form a framework. Examples include bridges, steel structures for buildings, and bicycle frames. In South Africa, consider the frame of a soccer goalpost or the steel scaffolding used during construction. Frame structures are efficient because they distribute the load across the members.

Shell Structures: These are hollow structures that derive their strength from their shape. Examples include eggshells, domes, and aircraft fuselages. Consider the corrugated iron sheeting frequently used for roofing in informal settlements, or the roof of a stadium. Shell structures are strong because the shape distributes the force over the entire surface.

Example: A school backpack. The fabric sides represent a shell structure (providing some structural support), while the internal frame (if present) represents a frame structure. The base is often reinforced as a solid structure. 2.2 Processing Systems All technological systems involve inputs, processes, and outputs.

Input: This is what is put into the system. It can be materials, energy, or information. For example, in a bread-making system, the inputs are flour, water, yeast, and heat.

Process: This is what happens to the input. It is the transformation of the input into an output. In the bread-making system, the process includes mixing the ingredients, kneading the dough, and baking it.

Output: This is what comes out of the system. It is the result of the process. In the bread-making system, the output is bread.

Example: A maize milling system in a rural South African community.

Input: Maize kernels, electricity (or manual labour).

Process: Grinding the maize kernels into maize meal using a milling machine.

Output: Maize meal. 2.3 Electronic Components Resistors: Resistors impede the flow of current in a circuit. They are measured in ohms (Ω). The larger the resistance, the lower the current flow. Resistors are crucial for controlling current flow and protecting other components in a circuit.

Capacitors: Capacitors store electrical energy in an electric field. They are measured in Farads (F). Capacitors can be used to filter signals, store energy, and provide temporary power.

LEDs (Light Emitting Diodes): LEDs are semiconductor devices that emit light when current flows through them in the forward direction. They are energy-efficient and have a long lifespan, making them ideal for lighting and indicator applications. LEDs only allow current to flow in one direction.

Transistors: Transistors are semiconductor devices that act as electronic switches or amplifiers. They control the flow of current between two points based on the current or voltage applied to a third point (the base or gate). They are the building blocks of modern electronic circuits. 2.4 Mechanisms and Motion Mechanisms are arrangements of components that transmit and/or transform motion.

Common types of motion include: Rotary Motion: Movement in a circular path (e.g., a bicycle wheel turning).

Linear Motion: Movement in a straight line (e.g., a sliding door).

Reciprocating Motion: Back-and-forth linear motion (e.g., a piston in an engine).

Oscillating Motion: Back-and-forth rotational motion (e.g., a pendulum swinging).

Example: The pedal of a bicycle creates rotary motion, which, through a chain and gears, is transferred to the rear wheel, also producing rotary motion. The pedals rotate around a fixed axis, and the rotating wheel moves the bicycle forward. 2.5 Control Systems Control systems are used to regulate and maintain a desired output.

There are two main types: Open-loop Control Systems: The output is not monitored or fed back into the system. The system operates based on pre-set instructions.

Examples: a toaster (time is set, but browning isn't monitored), a simple traffic light system with fixed timings.

Closed-loop Control Systems: The output is monitored and fed back into the system to adjust the input and maintain the desired output. This feedback loop allows for greater accuracy and stability.

Examples: a thermostat in an oven (temperature is constantly monitored and adjusted), a cruise control system in a car.