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

• Identify and explain mechanical systems like levers, gears, and pulleys.
• Apply the design process to solve a technological problem.
• Select appropriate materials based on their properties for a design.
• Explain how energy sources power technology and their environmental impact.

Lesson summary

This week, we will be revisiting and consolidating the key Technology concepts we have covered so far this term. This revision is crucial for solidifying your understanding of technological principles and their application in solving real-world problems. Technology is everywhere in South Africa, from cell phones and load shedding solutions to innovative farming techniques and water purification systems. A strong understanding of technology helps you become a creative problem-solver, a critical thinker, and an active participant in shaping South Africa's technological future.

Lesson notes

2.1 Mechanical Systems Explanation: Mechanical systems are collections of parts that work together to produce a desired movement or force. They are the foundation of many technologies we use daily. The main types are levers, linkages, gears, and pulleys.

Levers: A lever is a rigid bar that pivots around a fixed point (fulcrum) to multiply force. There are three classes of levers, distinguished by the relative positions of the fulcrum, load (resistance), and effort (force). Think of a see-saw (Class 1), a wheelbarrow (Class 2), and tweezers (Class 3).

Class 1: Fulcrum between load and effort.

Example: Crowbar, see-saw, pliers. These can provide mechanical advantage (making it easier to lift heavy things) or increase the distance the load moves.

Class 2: Load between fulcrum and effort.

Example: Wheelbarrow, bottle opener. These always provide mechanical advantage.

Class 3: Effort between fulcrum and load.

Example: Tweezers, fishing rod. These do not provide mechanical advantage, but they increase the distance and speed of the load.

Linkages: A linkage is a system of rigid bars connected by joints that transmit motion. They can change the direction, type, or magnitude of the motion. Consider a bicycle's gears and chains, or the suspension in a car. They transfer force and motion, and can transform rotary motion to linear motion, and vice-versa.

Example: A pantograph uses linkages to duplicate drawings at different scales.

Gears: Gears are toothed wheels that mesh together to transmit rotary motion. They can change the speed, torque (rotational force), and direction of rotation.

Gear Ratio: The gear ratio is the number of teeth on the driven gear divided by the number of teeth on the driving gear. A gear ratio greater than 1 increases torque and decreases speed. A gear ratio less than 1 increases speed and decreases torque.

Example: If a driving gear has 10 teeth and a driven gear has 20 teeth, the gear ratio is 20/10 =

2. This means the driven gear rotates half as fast as the driving gear but with twice the torque.

Pulleys: A pulley is a wheel with a grooved rim around which a rope, cable, or belt passes. Pulleys are used to lift heavy loads by changing the direction of the force or by providing mechanical advantage.

Fixed Pulley: A single pulley attached to a stationary object. It changes the direction of the force but does not provide mechanical advantage.

Movable Pulley: A pulley attached to the load being lifted. It provides mechanical advantage (reduces the amount of force needed to lift the load). The mechanical advantage is equal to the number of rope segments supporting the load.

Example: Lifting a bucket of water from a well (often uses a fixed pulley). Construction cranes use complex pulley systems to lift very heavy materials. 2.2 The Design Process Explanation: The design process is a systematic approach to solving problems and creating new products or systems.

It generally involves the following steps: Investigation: Identify the problem or need. Research existing solutions and gather information. Conduct surveys or interviews to understand the user's needs. Think about the context of the problem, e.g., is it about designing a water-saving device for drought-stricken areas?

Design: Generate different possible solutions. Sketch your ideas and create detailed drawings or models. Select the best design based on criteria such as cost, feasibility, and effectiveness. Consider aesthetics and ergonomics.

Make: Build a prototype or model of your design. Use appropriate tools and materials. Follow your design specifications carefully. Consider safety precautions.

Evaluate: Test your prototype and gather feedback. Identify areas for improvement. Consider its effectiveness and efficiency. Did it meet all original requirements?

Communicate: Share your design and results with others. Present your findings in a clear and concise manner. Write a report, create a presentation, or build a website. Why is the design process important in South Africa? South Africa faces numerous challenges, from water scarcity to reliable electricity supply. The design process can be used to develop innovative solutions to these problems. 2.3 Materials and Their Properties Explanation: The selection of appropriate materials is crucial in any design project. Different materials have different properties that make them suitable for different applications.

Key properties include: Strength: The ability of a material to withstand forces without breaking or deforming.

Flexibility: The ability of a material to bend or flex without breaking.

Hardness: The ability of a material to resist scratching or indentation.

Conductivity: The ability of a material to conduct heat or electricity.

Durability: The ability to withstand wear, pressure, or damage.

Corrosion Resistance: The ability to withstand rust or erosion in harsh environments.

Examples: Steel is strong and durable, making it suitable for bridges and buildings.