Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

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Performance objectives

• Define input, process, and output in a technological system.
• Identify and explain three types of structures and their stability.
• Describe the properties and uses of two common South African construction materials.
• Apply the concept of mechanical advantage using levers.
• Explain the importance of sustainable design and renewable energy.

Lesson summary

This week, we'll consolidate our Grade 7 Technology knowledge. We're reviewing previously covered concepts, focusing on strengthening your understanding and problem-solving skills. This is important because technology is increasingly integrated into every aspect of South African life, from agriculture and infrastructure to communication and entrepreneurship. Having a solid foundation in technological principles will empower you to be innovative, problem-solvers, and active participants in a technologically advancing society. By reviewing this material, you will also be better prepared for future Technology studies.

Lesson notes

2.1 Technological Systems: Input, Process, Output A technological system is a set of interconnected components that work together to transform inputs into outputs.

Input: What goes into the system (e.g., materials, energy, information). Think of the ingredients for a recipe.

Process: What happens inside the system – the actions, transformations, and operations. This is the "cooking" stage of the recipe.

Output: What comes out of the system (e.g., a product, a service, information). The finished dish.

Example 1: A Solar Water Heater (Relevant to South Africa)

Input: Sunlight (energy), Water (material), Metal pipes (material).

Process: Sunlight heats the metal pipes. The heat is transferred to the water. Hot water rises.

Output: Hot water.

Example 2: A Mobile Phone (Commonly Used)

Input: Electricity, User input (touch, voice), Digital data (images, sound).

Process: The phone processes the user input, accesses the internet, performs calculations, displays information.

Output: Communication (voice calls, messages), Information (web pages, apps), Entertainment (music, videos). 2.2 Structures: Types, Strength and Stability A structure is something that supports a load (weight or force). Different types of structures provide different levels of support and stability.

Frame Structure: Consists of connected parts (beams, columns) that create a framework. Think of a skeleton or a building's steel frame. Strength comes from the connections and the materials used.* Shell Structure: A hollow structure made from a curved surface. Think of an eggshell or a dome. Strength comes from the shape, which distributes the load.* Solid Structure: A structure made from a solid material. Think of a brick wall or a statue. Strength comes from the inherent strength of the material.* Mass Structure: Structures made by piling up loose materials. Think of a dam or a pyramid. Strength comes from the weight of the materials and their arrangement.* Stability is the ability of a structure to resist being overturned or collapsing. A wider base generally increases stability.

Example: Consider building a small shed. A frame structure using wooden planks will be strong, but requires careful construction. A solid structure using bricks will also be strong, but is more resource-intensive. 2.3 Materials: Properties and Uses Different materials have different properties that make them suitable for different purposes. Common building materials in South Africa include: Wood: Relatively lightweight, easy to work with, renewable (if sustainably sourced), but can be susceptible to rot and fire.

Uses:* Framing, furniture, cladding.

Concrete: Strong in compression (withstanding crushing forces), durable, relatively inexpensive, but heavy and can crack.

Uses:* Foundations, walls, roads, bridges.

Steel: Very strong in both tension (withstanding pulling forces) and compression, durable, but can rust.

Uses:* Reinforcing concrete, structural beams, bridges, roofing.

Recycled Plastics: Lightweight, durable, weather resistant, can be made into bricks and other construction materials, helps reduce plastic waste.

Uses:* Fencing, paving, bricks, furniture.

Example: When building a house, concrete is often used for the foundation because it can withstand the weight of the building. Steel is used to reinforce the concrete, adding tensile strength. Wood can then be used for the framing and roofing. 2.4 Levers and Mechanical Advantage A lever is a simple machine that makes work easier by multiplying force. It consists of a rigid bar that pivots around a fixed point called a fulcrum.

Fulcrum: The pivot point.

Load: The object being moved or lifted.

Effort: The force applied to move the load. Mechanical Advantage (MA) = Load / Effort A lever with a high mechanical advantage allows you to lift a heavy load with less effort.

Example: Imagine using a crowbar (lever) to lift a heavy rock. The fulcrum is placed close to the rock (load). You apply effort to the other end of the crowbar. Because the distance from the fulcrum to your effort is much greater than the distance from the fulcrum to the load, you get a mechanical advantage. You can lift the rock with less force than its actual weight.