Lesson Notes By Weeks and Term v5 - Grade 7

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

• Define and classify structures (frame, shell, solid).
• Explain a system's input, process, and output.
• Describe how processing changes materials.
• Apply knowledge of mechanisms like levers and gears.
• Identify components in a simple electrical circuit.

Lesson summary

This week, we will be consolidating our understanding of various Technology topics covered so far this year. This revision is crucial because Technology provides us with the knowledge and skills to solve everyday problems, design and create innovative solutions, and understand how things work around us. In South Africa, where innovation and sustainable development are vital for our future, having a strong foundation in Technology is essential for every learner. We'll be revisiting concepts from structures, processing, systems, and control, ensuring we have a solid understanding before moving forward.

Lesson notes

A. Structures: Structures are objects designed to support loads. They can be categorized into three main types: Frame Structures: These structures are made up of many individual parts joined together to form a strong, rigid framework. Examples include bridges, buildings, towers, and bicycle frames. The strength relies on how the parts are arranged and connected. Think about the shacks in informal settlements - often using scrap wood or metal in frame-like formations. Understanding how these structures work is essential to ensuring they are safe and stable.

Shell Structures: These structures use a thin, curved outer layer to provide strength and support. Examples include eggshells, domes, aircraft fuselages, and even corrugated iron roofs. The curved shape distributes the load evenly, making them very strong for their weight.

Look at traditional rondavels: their rounded walls provide structural integrity and resistance to strong winds.

Solid Structures: These structures are made from a single piece of material. Examples include a solid concrete pillar, a wooden beam, or a rock. The strength of the structure depends on the properties of the material itself. A brick wall is a good example - each brick acting as a solid unit in the overall structure.

Example: Consider a stadium. The seating area and roof often use frame structures for support, while the dome-shaped roof might be a shell structure. The concrete pillars supporting the entire structure are solid structures.

B. Systems and Control: A system is a set of components that work together to achieve a specific goal.

The basic elements of a system are: Input: What goes into the system (e.g., electricity, raw materials, information).

Process: What the system does with the input (e.g., heating, manufacturing, calculating).

Output: What the system produces as a result of the process (e.g., light, a finished product, a calculation result).

Feedback: Information from the output that is used to adjust the input or process to improve the system's performance.

Example: A water purification system used in many South African communities.

Input: Contaminated water.

Process: Filtration, chemical treatment (e.g., chlorination), UV disinfection.

Output: Clean, drinkable water.

Feedback: Testing the water quality and adjusting the amount of chlorine added to maintain safety.

C. Processing: Processing involves changing the properties of materials to make them more useful.

Common processing techniques include: Heating: Can soften metals, cure plastics, or cook food. For example, heating clay in a kiln to create pottery.

Cooling: Can harden metals, set concrete, or preserve food. Freezing meat to keep it fresh for longer is a good example.

Bending: Can change the shape of metal, wood, or plastic. Bending sheet metal to create car body panels.

Cutting: Separates materials into smaller pieces. Using a saw to cut wood for furniture.

Joining: Fastens materials together using adhesives, welding, or fasteners like screws and bolts. Welding metal pipes together for a water pipeline.

Example: Making mielie meal (maize flour): The process involves harvesting maize (input), grinding the maize kernels (process), and producing mielie meal (output).

D. Mechanisms: Mechanisms are devices that change motion and force.

Common types of mechanisms include: Levers: A rigid bar that pivots around a fixed point (fulcrum) to multiply force.

Examples: seesaw, crowbar, bottle opener.

Gears: Toothed wheels that mesh together to transmit rotational motion and change speed or torque.

Examples: bicycle gears, car gearbox.

Linkages: Systems of interconnected rods (links) that transmit motion in a specific way.

Examples: bicycle brakes, windscreen wipers.

Example: A bicycle uses gears to allow the rider to pedal at a comfortable rate while travelling at different speeds. Levers are used in the brakes to apply force to the wheels and stop the bicycle.

E. Electrical Systems: An electrical circuit is a closed loop that allows electricity to flow.

Key components include: Power Source: Provides the electrical energy (e.g., battery, power outlet).

Conductor: A material that allows electricity to flow easily (e.g., copper wire).

Load: A device that uses the electrical energy (e.g., light bulb, LED).

Switch: A device that can open or close the circuit to control the flow of electricity.

Resistor: A component that limits the flow of current.

Example: A simple circuit to light an LED: A battery (power source) is connected to an LED (load) with wires (conductors). A resistor is included to limit the current flowing through the LED and protect it from burning out. A switch can be added to turn the LED on and off. Guided Practice (With Solutions)

Question 1: Identify the type of structure used in a typical cell phone tower. Explain why that type of structure is suitable.

Solution: Cell phone towers are primarily frame structures.