Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

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Performance objectives

• Describe the stages of the Technological Process.
• Explain the function of levers, gears, and pulleys.
• Differentiate between common materials and their properties.
• Demonstrate basic sketching techniques.
• Explain the importance of safety precautions.

Lesson summary

This week in Technology, we'll be consolidating all the knowledge and skills we've built up so far this year. This revision is crucial because it reinforces understanding and helps us apply what we've learned to solve real-world problems. Think about how technology impacts everything from the houses we live in, the food we eat (farming technology!), to the way we communicate with each other. By mastering these foundational concepts, you will be better equipped to design, create, and innovate solutions that address challenges in our communities and the wider world.

Lesson notes

Let's dive into the core concepts we've covered. a)

The Technological Process: The Technological Process is a systematic approach to solving problems using technology.

It consists of several key stages: Investigate: This is where we identify the problem, research existing solutions, and gather information. For example, imagine a community in rural Limpopo struggling to access clean water. We would investigate the water sources, the needs of the community, and existing water purification technologies.

Design: Based on our investigation, we brainstorm possible solutions, sketch out our ideas, and create detailed plans. This stage involves considering factors like cost, availability of materials, and environmental impact. We might design a solar-powered water purification system.

Make: This is the construction phase. We build a prototype or model of our design using appropriate tools and materials. In our water purification example, this involves assembling the components of the system according to our design.

Evaluate: Once the prototype is built, we test it thoroughly to see if it meets our requirements. We identify any flaws and make improvements. We would test the water purified by our system to ensure it's safe to drink and evaluate the system's efficiency.

Communicate: Finally, we share our findings with others, explaining our design process, the challenges we faced, and the results we achieved. This can involve creating presentations, writing reports, or demonstrating our solution. b)

Simple Mechanical Systems: These are fundamental building blocks of many complex machines.

Levers: A lever is a rigid bar that pivots around a fixed point called a fulcrum. Levers are used to multiply force. There are three classes of levers, defined by the relative positions of the fulcrum, the effort (force you apply), and the load (the object you're moving).

Example: A seesaw is a classic example of a Class 1 lever (fulcrum in the middle). A wheelbarrow is a Class 2 lever (load in the middle). A pair of tweezers is a Class 3 lever (effort in the middle).

Calculation: The mechanical advantage (MA) of a lever is calculated as: MA = Distance from effort to fulcrum / Distance from load to fulcrum. A lever with an MA greater than 1 allows you to lift a heavier load with less effort.

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

Example: Gears are found in bicycles, cars, and clocks.

Imagine a bicycle: the gears allow you to pedal at a comfortable rate while still moving the wheels at a different speed.

Calculation: The gear ratio is the ratio of the number of teeth on the driven gear (output) to the number of teeth on the driving gear (input). Gear Ratio = Number of teeth on driven gear / Number of teeth on driving gear. If the gear ratio is greater than 1, the output speed is lower, but the output torque is higher. If the gear ratio is less than 1, the output speed is higher, but the output torque is lower.

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

Example: Pulleys are used in cranes, elevators, and flagpoles.

Calculation: The mechanical advantage of a pulley system depends on the number of rope segments supporting the load. In a simple pulley system (a single fixed pulley), the mechanical advantage is 1 (it just changes the direction of the force). In a system with multiple pulleys (a block and tackle), the mechanical advantage is equal to the number of rope segments supporting the load. c)

Materials and Their Properties: Different materials have different properties that make them suitable for different applications.

Important properties include: Strength: The ability of a material to withstand force without breaking.

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

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

Durability: The ability of a material to withstand wear and tear over time.

Water Resistance: The ability of a material to resist water damage.

Thermal Conductivity: The ability of a material to conduct heat.

Examples: Wood is strong and durable, making it suitable for furniture and construction. Steel is very strong and hard, making it suitable for bridges and tools. Plastic is lightweight and water-resistant, making it suitable for containers and packaging. Consider using recycled materials in projects whenever possible, promoting sustainability. d)

Sketching and Drawing Techniques: Sketching is a quick and easy way to visualize and communicate your ideas.

Basic techniques include: Freehand sketching: Drawing without using any measuring tools.

Orthographic projection: Drawing multiple views of an object (front, top, side) to show its shape and dimensions accurately.