Lesson Notes By Weeks and Term v5 - Grade 9

Lesson Video

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Performance objectives

• Explain mechanical systems like levers, linkages, and gears.
• Describe properties and uses of different materials.
• Apply the 5 steps of the design process.
• Explain the impact of technology on society.
• Understand basic principles of electricity.

Lesson summary

This week focuses on revising key concepts from the Grade 9 Technology curriculum in preparation for upcoming assessments. Technology surrounds us, from the cellphones we use to communicate to the infrastructure that provides us with water and electricity. Understanding the principles behind these technologies is crucial for navigating the modern world and contributing to South Africa's development. Many of the challenges facing South Africa, such as energy security, water scarcity, and affordable housing, require innovative technological solutions. This revision will equip you with the knowledge and skills to become problem-solvers and innovators in your communities.

Lesson notes

Mechanical Systems: Definition: Mechanical systems are systems that use mechanical energy to perform a task. They typically involve moving parts that transmit forces and motion.

Levers: A lever is a rigid bar that pivots around a fixed point called a fulcrum. There are three classes of levers, distinguished by the relative positions of the fulcrum, load (resistance), and effort (force). Examples in South Africa include crowbars (used for construction), wheelbarrows (used in gardens and construction), and seesaws (playgrounds).

Mechanical Advantage (MA): MA is the ratio of the output force (load) to the input force (effort). MA = Load / Effort If MA > 1, the lever multiplies the force. If MA < 1, the lever increases the distance or speed.

Linkages: Linkages are systems of rigid bars connected by joints (pivots). They are used to transmit motion and change its direction or magnitude. Examples include bicycle brakes, windscreen wipers, and the suspension systems in vehicles.

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: Gear Ratio = Number of teeth on driven gear / Number of teeth on driving gear. If the gear ratio is greater than 1, the speed decreases, and the torque increases. If the gear ratio is less than 1, the speed increases, and the torque decreases.