Lesson Notes By Weeks and Term v5 - Grade 7

Lesson Video

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Performance objectives

• Identify and describe types of structures (frame, shell, solid).
• Explain how to strengthen structures (triangulation, thicker materials, folding).
• Identify functions of mechanisms (levers, gears, pulleys, linkages).
• Apply the concepts of input, process, and output.
• Explain how to improve existing designs based on criteria.

Lesson summary

This week, we'll be revising and consolidating key concepts from our Grade 7 Technology curriculum. Technology surrounds us, from the cell phones we use to communicate to the infrastructure that provides us with water and electricity. Understanding technological processes and design principles is crucial for participating effectively in the modern world and contributing to the growth of South Africa. We'll be focusing on structures, mechanisms, and processing. This week's lesson prepares you for further studies in Technology and equips you with valuable problem-solving skills that can be applied in various aspects of your life.

Lesson notes

Structures A structure is something that supports a load or contains something.

There are three main types of structures: Frame Structures: These structures have a skeleton-like framework of interconnected members (beams, columns, etc.) that support the load. Think of the Eiffel Tower or a bicycle frame.

Advantages:* Strong for their weight, can span large distances.

Disadvantages:* Can be complex to build, susceptible to buckling under compression.

Shell Structures: These structures use a thin, curved outer surface to support the load. Think of an eggshell or a dome.

Advantages:* Strong for their weight, can distribute loads evenly.

Disadvantages:* Can be difficult to manufacture, vulnerable to concentrated loads.

Solid Structures: These structures are made of solid material throughout. Think of a brick wall or a dam wall.

Advantages:* Simple to build, robust.

Disadvantages:* Heavy, uses a lot of material.

Strengthening Structures: Triangulation: Using triangles in a structure makes it much stronger and more rigid because triangles are inherently stable shapes. Think of the support beams on a bridge or a radio tower.

Using Thicker Materials: Increasing the thickness of the material used to build a structure increases its strength and resistance to bending and breaking. A thicker steel beam is stronger than a thinner one.

Folding: Folding a flat sheet of material creates creases that act as stiffeners, increasing the structure's overall strength and rigidity. Think of how corrugated cardboard is stronger than a flat sheet of cardboard.

Example 1: Comparing Structures Consider a spaza shop. The walls are typically made of bricks (solid structure), while the roof often uses a frame structure with corrugated iron sheets. The brick walls provide robustness and security, while the frame and corrugated iron roof offer lightweight protection from the weather. Mechanisms A mechanism is a device that changes movement. They are used to transfer force and motion, often making work easier.

Common mechanisms include: Levers: A rigid bar that pivots on a fixed point (fulcrum). Levers can be used to multiply force.

Examples: a see-saw, a bottle opener.

Gears: Toothed wheels that mesh together to transmit rotary motion. Gears can change speed, torque (turning force), and direction of rotation.

Examples: a bicycle, a clock.

Pulleys: A wheel with a grooved rim around which a rope or belt passes. Pulleys can be used to change the direction of a force or to multiply force.

Examples: a flagpole, a crane.

Linkages: A system of rigid bars connected by joints. Linkages can convert one type of motion into another.

Examples: bicycle brakes, windscreen wipers.

Example 2: Lever Application Imagine you are trying to move a heavy rock in your garden using a long wooden plank (lever) and a smaller rock as a fulcrum. By placing the fulcrum closer to the heavy rock, you can use less force to lift it because the lever multiplies your effort. This is how levers make work easier.

Example 3: Gear Application In a bicycle, different sized gears are used to change the speed and force applied to the wheels. When climbing a hill, you shift to a lower gear (larger gear at the back, smaller gear at the pedals) to increase the torque and make it easier to pedal, even though you are moving slower. Processing Processing involves taking an input, performing an action or transformation (the process), and producing an output. This concept is fundamental to understanding how technological systems work, particularly in areas like computer programming.

Input: Data or resources that enter a system.

Examples: pressing a button, typing on a keyboard, raw materials.

Process: The action or transformation performed on the input.

Examples: calculations, sorting, manufacturing.

Output: The result of the process.

Examples: a light turning on, text displayed on a screen, a finished product.

Example 4: Processing in a Toaster Input: Bread, electricity, pressing the lever.

Process: Heating elements toast the bread.

Output: Toasted bread.

Example 5: Processing in a cellphone game: Input: Touching the screen.

Process: The game registers where and when you touch the screen, applies game logic (e.g., moves a character, fires a weapon).

Output: The game displays the result (e.g., the character moves, an enemy is defeated), sound effects play. Guided Practice (With Solutions)

Question 1: Identify the type of structure used in the following: a suspension bridge, a soccer ball, and a stack of books. Explain why that type of structure is appropriate in each case.

Solution: Suspension Bridge: Frame structure. Frame structures are ideal for spanning long distances, and the suspension cables efficiently distribute the load.

Soccer Ball: Shell structure. Shell structures are strong and lightweight, making them suitable for containing air pressure and withstanding impacts.

Stack of Books: Solid structure. Solid structures are simple and robust for bearing weight directly.