Lesson Notes By Weeks and Term v5 - Grade 9

Lesson Video

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Performance objectives

• Define and apply the steps of the design process.
• Identify and classify materials based on their properties.
• Explain and calculate mechanical advantage in simple systems.

Lesson summary

This week focuses on reviewing key concepts from the Grade 8 and 9 Technology curriculum to prepare for upcoming assessments. Technology is essential for innovation and development in South Africa, from improving infrastructure and agriculture to creating new business opportunities and addressing societal challenges like access to clean water and energy. Understanding the principles of design, materials, systems, and control is critical for building a brighter future for our communities. This revision will sharpen your understanding of these areas and boost your confidence when tackling complex problems and design challenges.

Lesson notes

2.1 The Design Process The design process is a systematic approach to solving problems and creating solutions. It's not just about making something look good; it's about understanding the problem, generating ideas, building a prototype, testing it, and improving it.

The five main steps are: Investigation: This is where you identify the problem, research existing solutions, and define the needs and constraints. This includes talking to potential users and gathering information to understand the problem thoroughly. For example, imagine a school in a rural area needs a better way to access clean drinking water. During the investigation phase, you would investigate the current water source, its contamination levels, the number of people who need access, and any existing water purification solutions.

Design: Brainstorming possible solutions, sketching ideas, and creating detailed drawings. This is where creativity comes in! You would explore various solutions, like rainwater harvesting, solar-powered water pumps, or a simple filtration system using locally available materials. You would then sketch out several designs and choose the most feasible one.

Making: This is where you build a prototype or model of your design. It's important to use appropriate tools and materials safely. If you chose a filtration system, you would gather materials like sand, gravel, charcoal, and a container to build a working model.

Evaluation: Test your prototype and identify any weaknesses or areas for improvement. Does it meet the original needs? What works well? What doesn't? You would test the water filtered by your system and compare it to the original water source. You would note the clarity, taste, and any remaining contaminants.

Communication: Share your design and findings with others. This could be through a presentation, report, or demonstration. You would create a presentation to show the problem, your design, the testing results, and any recommendations for improvement. 2.2 Materials and Their Properties Materials are the building blocks of technology. Understanding their properties is crucial for selecting the right material for a specific task.

Key properties include: Strength: The ability to withstand force without breaking.

Hardness: Resistance to scratching or indentation.

Ductility: The ability to be stretched into a wire.

Malleability: The ability to be hammered into thin sheets.

Conductivity: The ability to conduct electricity or heat.

Density: Mass per unit volume.

Common materials and their uses: Wood: Used for furniture, construction, and tools. Different types of wood have different properties. For example, pine is softwood, easily worked with, and used for simple construction, while hardwood like oak is stronger and used for furniture.

Metal: Used for tools, structures, and electronics. Steel is strong and versatile, while aluminum is lightweight and corrosion-resistant. Copper is an excellent conductor of electricity and is used in wiring.

Plastic: Used for packaging, containers, and components. Plastics can be molded into complex shapes and are often lightweight and inexpensive. Different types of plastics exist, each with different properties (e.g., polyethylene, polypropylene, PVC).

Composites: Made by combining two or more materials to create a new material with improved properties. An example is fiberglass, which combines glass fibers with a resin matrix. This results in a material that is strong and lightweight, often used in boat hulls. 2.3 Simple Mechanical Systems Simple machines are basic mechanical devices that multiply force or change the direction of force. They make work easier.

Levers: A rigid bar that pivots around a fixed point (fulcrum). There are three classes of levers depending on the relative positions of the load, effort, and fulcrum. Mechanical Advantage (MA) = Load / Effort = Distance from Effort to Fulcrum / Distance from Load to Fulcrum

Example:* A crowbar used to lift a heavy rock. If the distance from the effort (where you push) to the fulcrum is 1 meter, and the distance from the load (the rock) to the fulcrum is 0.2 meters, then MA = 1/0.2 =

5. This means you only need to apply one-fifth of the rock's weight to lift it.

Pulleys: A wheel with a grooved rim around which a rope, cable, or belt passes. They change the direction of force and can also multiply force. Mechanical Advantage (MA) = Number of rope segments supporting the load

Example:* A pulley system used to lift a bucket of water from a well. If there are 3 rope segments supporting the bucket, the MA =

3. This means you only need to pull with one-third of the bucket's weight to lift it.

Gears: Toothed wheels that mesh together to transmit rotary motion and force. They can change speed and direction of rotation. Mechanical Advantage (Gear Ratio) = Number of teeth on driven gear / Number of teeth on driving gear

Example:* A bicycle. The front gear (driving gear) has 48 teeth and the rear gear (driven gear) has 16 teeth.

Reference guide

• (e.g., wooden planks, metal pipes).
• Making: The farmer builds a prototype of the lever system using the chosen materials. He ensures the lever is strong enough to support the weight of the bags.
• Evaluation: The farmer tests the lever system by lifting bags of fertilizer. He checks if it is easy to use and if it effectively reduces the effort required. He identifies any weaknesses, such as the lever being too short or the platform being unstable.
• Communication: The farmer shares his design with other farmers and gets feedback. He documents the process and explains the advantages and limitations of his solution.
• Question 2: A pulley system is used to lift a 100 N load. If the system has a mechanical advantage of 4, what is the effort required to lift the load?
• Solution: