Lesson Notes By Weeks and Term v4 - JHS 3

Lesson Video

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Performance objectives

• Identify simple structures and mechanisms.
• Design a simple technology project.
• Construct a basic model of your project.
• Explain and evaluate your project's functionality.

Lesson summary

Welcome, learners! In our previous lessons, we learned about individual simple machines like levers, pulleys, and gears. However, almost every machine we use in Ghana, from a simple bicycle to a complex corn mill, is not just one simple machine. They are clever combinations of several mechanisms working together to perform a useful task. This lesson is very practical. We will move beyond just identifying mechanisms and learn how to think like engineers and inventors. We will learn the process of designing and then making our own simple projects by combining at least two different mechanisms. This skill is crucial for solving everyday problems and for creating new technologies.

Lesson notes

A. Recap: What are Simple Mechanisms?

A mechanism is a device that transmits or changes motion and force. Simple mechanisms are the basic building blocks of all machines.

| Mechanism | Description | Ghanaian Example | | :--- | :--- | :--- | | Lever | A rigid bar that pivots around a fixed point called a fulcrum. | A seesaw in a school park; using a crowbar to remove a stump. | | Pulley | A wheel with a groove for a rope or cable. It changes the direction of force and can give a mechanical advantage. | The system used on a flagpole to raise the flag; a "Kufuor gallery" clothesline. | | Wheel & Axle | A large wheel fixed to a smaller rod (axle). When one turns, the other turns. | The steering wheel of a car (trotro); the handle of a door. | | Gears | Toothed wheels that mesh together to transfer motion and change speed or direction. | The gears on a bicycle; the inside of an eggbeater. | | Inclined Plane | A flat, sloped surface. It makes it easier to move an object to a higher or lower level. | A ramp for a wheelchair; a slide in a playground. | | Wedge | Two inclined planes joined back-to-back. Used to separate or hold objects. | The blade of an axe used to split firewood; a doorstop. | | Screw | An inclined plane wrapped around a cylinder. Used to fasten things or lift objects. | The cap of a water bottle; a carpenter's screw. | | Linkages | A system of connected bars that can move and change the direction of motion. | The mechanism that moves the wipers on a car windscreen. | B. The Power of Combination: Why Combine Mechanisms?

Imagine you want to build a machine to fetch water from a deep well and pour it into a bucket on the ground. You could use a pulley to lift the water up easily. But how do you get it to swing over and tip into your bucket? You could attach the pulley system to a long arm that can rotate. This arm is a lever.