Tech

Got you. I’ll redo all 25 topics in your exact order, without skipping or combining repeated topics. Each definition will be about two sentences, followed by the important facts, examples, formulas or diagrams you need for your Grade 9 Technology exam.

Grade 9 Technology — Term 4 Study Notes

1. Orthographic drawings

Definition: An orthographic drawing is a technical drawing that shows an object from different directions using separate, flat views. These views help someone understand the object’s shape and dimensions accurately without seeing it in 3D.

The three main views:

• Front view: Shows the object as seen from the front.

• Top view (plan): Shows the object from above.

• Side view: Shows the object from the left or right side.

Important rules:

• The views must line up correctly with one another.

• Dimensions show measurements such as length, width and height.

• Use the correct line types for visible edges, hidden details and measurements.

• Orthographic drawings are different from isometric drawings, which show an object in a 3D-like view.

Exam tip: If asked to draw orthographic views, keep the views aligned and include all the required dimensions.

2. Properties of various construction materials

Definition: Material properties describe how a material behaves when forces, heat, water or other conditions affect it. These properties help engineers choose suitable materials for buildings, bridges, tools and other structures.

Examples:

• Steel is used in structural frames because it is strong.

• Concrete is used in foundations because it withstands compression well.

• Rubber is useful for seals because it is flexible.

• Glass is useful for windows because it is transparent, but it is relatively brittle.

Exam tip: When asked why a material is suitable, name the property and explain how it helps in that application.

3. Pascal’s principle

Definition: Pascal’s principle states that pressure applied to an enclosed liquid is transmitted equally throughout the liquid and to the walls of its container. This principle allows a small input force on a small piston to produce a larger output force on a larger piston.

Important terms:

• Pressure: Force applied per unit area.

• Force: A push or pull, measured in newtons (N).

• Area: The surface area over which a force acts.

• Hydraulic fluid: A liquid used to transmit pressure in a hydraulic system.

Formula:

P=\frac{F}{A}

Where:

• = pressure

• = force

• = area

In a simple ideal hydraulic system:

\frac{F_1}{A_1}=\frac{F_2}{A_2}

Example: If the output piston has ten times the area of the input piston, the output force can be ten times the input force, assuming an ideal system.

Applications: Hydraulic jacks, hydraulic presses, vehicle brakes and lifting equipment.

Exam tip: Pascal’s principle is about pressure being transmitted through an enclosed liquid; it does not mean the force stays the same on pistons of different sizes.

4. Gears

Definition: Gears are toothed wheels that mesh together to transfer rotational movement and force from one shaft to another. They can change the speed, direction and turning force of a mechanism.

Important terms:

• Driver gear: The gear that supplies the movement.

• Driven gear: The gear receiving the movement.

• Teeth: The projections that mesh with the teeth of another gear.

• Gear ratio: The relationship between the number of teeth on the gears.

For two meshing gears:

\text{Gear ratio}=\frac{\text{Teeth on driven gear}}{\text{Teeth on driver gear}}

To calculate the driven gear’s number of turns:

\text{Driven turns}=
\text{Driver turns}\times
\frac{\text{Driver teeth}}{\text{Driven teeth}}

Worked example:

A 12-tooth driver gear turns 3 times and drives a 36-tooth gear.

3\times\frac{12}{36}=1\text{ turn}

The driven gear turns once.

Rules to remember:

• Two externally meshing gears turn in opposite directions.

• A larger driven gear turns more slowly but can provide greater turning force.

• A smaller driven gear turns faster but generally provides less turning force.

• Gear systems are used in bicycles, clocks, vehicles and machinery.

5. Ratchet and pawl

Definition: A ratchet and pawl is a mechanism that allows movement in one direction while preventing or restricting movement in the opposite direction. It uses a toothed wheel called a ratchet and a small catch called a pawl.

Main parts:

• Ratchet wheel: Has angled or specially shaped teeth.

• Pawl: Engages with the teeth to stop reverse movement.

• Spring: Often keeps the pawl pressed against the wheel.

How it works:

• The ratchet wheel rotates in the permitted direction.

• The pawl moves over the teeth as the wheel turns.

• If the wheel tries to turn backwards, the pawl catches against a tooth and prevents reverse rotation.

Applications:

• Socket wrenches

• Winches

• Bicycle freewheel mechanisms

• Some lifting and locking devices

Advantages: It can hold a mechanism in position and allow controlled movement in one direction.

Exam tip: Remember the key function: one-way movement. A ratchet and pawl does not automatically make a system hydraulic or increase its force.

6. Hydraulic press

Definition: A hydraulic press uses pressure transmitted through a liquid to produce a large force for pressing, shaping or compressing materials. It works according to Pascal’s principle, using a small input piston and a larger output piston.

Main components:

• Input piston or pump

• Hydraulic liquid

• Connecting pipes or passages

• Larger output piston

• Strong frame

• Valves to control the liquid

How it works:

• A force is applied to the small input piston.

• The piston creates pressure in the enclosed hydraulic liquid.

• The pressure is transmitted through the liquid.

• The larger output piston produces a greater force.

• The output force presses or compresses the material.

Formula:

\frac{F_1}{A_1}=\frac{F_2}{A_2}

Example: If the output piston has five times the area of the input piston, an ideal press can produce five times the input force.

Uses: Pressing metal sheets, shaping materials, compressing objects and industrial manufacturing.

Advantages: It produces large forces and can apply pressure in a controlled way.

Limitation: The larger force comes with a distance trade-off: in an ideal system, the output piston moves a shorter distance than the input piston.

7. Hydraulic jack

Definition: A hydraulic jack is a lifting device that uses liquid pressure to raise a heavy load, such as part of a vehicle. A small input force acts on a pump piston, and the hydraulic liquid transfers pressure to a larger lifting piston called a ram.

Main parts:

• Handle: Operates the pump in many manual jacks.

• Pump piston: Pushes hydraulic fluid into the system.

• Hydraulic fluid: Transfers pressure.

• Valves: Control the movement of the fluid.

• Ram or lifting piston: Moves upwards to lift the load.

• Reservoir: Stores hydraulic fluid in many designs.

• Release valve: Allows fluid to return so the jack can lower.

How it works:

• The handle operates the pump piston.

• The pump pushes fluid through a one-way valve.

• Pressure builds in the lifting chamber.

• The larger ram moves upwards and raises the load.

• Opening the release valve allows fluid to return, lowering the load.

Formula:

F_{\text{out}}=F_{\text{in}}\times
\frac{A_{\text{out}}}{A_{\text{in}}}

Worked example:

Input force = 30 N, input area = 6 cm², output area = 60 cm².

F_{\text{out}}=30\times\frac{60}{6}F_{\text{out}}=300\text{ N}

The ideal output force is 300 N.

Uses: Lifting vehicles for maintenance and raising heavy equipment.

Safety: A vehicle must be supported by suitable safety stands before anyone works underneath it; a hydraulic jack alone is not a safe support.

8. Pneumatic system

Definition: A pneumatic system uses compressed air or another gas to transmit energy and operate machinery. The compressed gas moves through pipes and valves to control a device such as a cylinder or air-powered tool.

Main components:

• Compressor: Compresses air.

• Air reservoir: Stores compressed air.

• Pipes or hoses: Carry the air.

• Valves: Control the direction and flow of air.

• Actuator: Converts the air pressure into movement, often using a cylinder or motor.

How it works:

• The compressor draws in air and compresses it.

• The compressed air is stored or supplied to the system.

• A valve directs the air to the actuator.

• The air pressure moves the actuator.

• The air is released or exhausted after use.

Advantages:

• Air is widely available.

• Systems can respond quickly.

• Air leaks are generally less messy than hydraulic-fluid leaks.

Disadvantages:

• Compressed air can be noisy.

• Leaks waste energy.

• Air is compressible, so movement may be less rigid and precise than in many hydraulic systems.

Applications: Air brakes, pneumatic tools, factory automation and automatic doors.

9. Preserving materials

Definition: Preserving materials means protecting them from damage caused by water, air, chemicals, sunlight, pests or general wear. The correct preservation method depends on the material and the type of damage that must be prevented.

Common methods:

Why preservation matters:

• It increases the useful life of materials.

• It reduces maintenance and replacement costs.

• It can improve safety by preventing material deterioration.

Exam tip: Do not just name the method. Explain what it protects against, such as rust, moisture, rot or wear.

10. Load and force

Definition: A force is a push or pull that can change an object’s movement or shape, and it is measured in newtons (N). A load is the force or weight that a structure, machine or component must support or move.

Important distinctions:

• Mass: Amount of matter in an object, measured in kilograms (kg).

• Weight: The gravitational force acting on an object, measured in newtons (N).

• Load: The force placed on a structure or mechanism.

• Effort/input force: The force applied to operate a machine.

• Output force: The force produced by the machine.

Types of force:

• Compression: Pushes or squeezes a material.

• Tension: Pulls or stretches a material.

• Shear: Forces act in opposite directions across a material.

• Torsion: Twists a material.

• Bending: Causes a material to curve.

Moment of a force: A moment describes the turning effect of a force around a pivot.

\text{Moment}=\text{Force}\times
\text{perpendicular distance from pivot}

Moment is measured in newton-metres (N·m).

Worked example:

A force of 40 N acts 0.5 m from a pivot.

M=40\times0.5=20\text{ N·m}

The moment is 20 N·m.

Exam tip: Use the perpendicular distance from the pivot, not just any distance given in the question.

11. Electrical/electronic system

Definition: An electrical system uses electrical energy to perform a task, such as producing light, heat or movement. An electronic system uses components to control or process electrical signals, often to make decisions or control another device.

The input-process-output system:

• Input: A signal or energy enters the system.

• Process: Components act on the input.

• Output: The system produces a result.

Example — automatic streetlight:

Electrical components:

• A cell or battery supplies electrical energy.

• Wires provide a path for current.

• A switch opens or closes the circuit.

• A bulb converts electrical energy into light and heat.

• A resistor limits or controls current.

Electronic components: Components such as resistors, diodes, transistors and sensors can control the flow of current or process signals.

Exam tip: If asked to identify input, process and output, explain the role each part plays in the particular system.

12. Types of lines

Definition: Technical drawings use different line types to communicate the shape, position and dimensions of an object. Using the correct line type makes a drawing clear and prevents confusion about which edges are visible or hidden.

Important rules:

• Visible outlines should stand out from construction and dimension lines.

• Dimension lines should be clear and should not be confused with object outlines.

• Hidden-detail lines show features behind a visible surface.

• Centre lines help identify the centre of holes, circles and symmetrical objects.

Exam tip: Learn both the appearance and purpose of each line type. If the question gives a drawing, identify the line by how it looks and what it represents.

13. Pulleys

Definition: A pulley is a wheel with a groove around its edge that guides a rope, cable or belt. Pulleys can change the direction of a force and, when arranged in a system, reduce the input force needed to lift a load.

Types of pulleys:

• Fixed pulley: Attached to a stationary support; mainly changes the direction of the effort. Its ideal mechanical advantage is 1.

• Movable pulley: Moves with the load and can reduce the force required to lift it.

• Compound pulley or block and tackle: Combines fixed and movable pulleys to make lifting heavier loads easier.

Mechanical advantage of an ideal pulley system:

MA=\text{number of rope sections supporting the load}

This shortcut applies to an ideal pulley arrangement. Friction and the weight of the pulley parts affect real performance.

Example: If four rope sections support the moving load, the ideal mechanical advantage is 4. This means the input force can be approximately one-quarter of the load force, but the rope must be pulled a greater distance.

Applications: Cranes, flagpoles, lifts, sailing equipment and construction machinery.

Exam tip: Count the rope sections supporting the moving load, not simply the number of pulley wheels.

14. Plastics

Definition: Plastics are materials made mainly from polymers, which are long chains of molecules. They can be manufactured with different properties, making them useful for products that need to be lightweight, mouldable, waterproof or electrically insulating.

Common properties of plastics:

• Usually lightweight.

• Often resistant to water and corrosion.

• Can be moulded into many shapes.

• Many plastics are good electrical insulators.

• Some are flexible, while others are rigid.

• Some withstand heat better than others, but many soften or deform at high temperatures.

Examples and uses:

Advantages: Plastics can be inexpensive to produce, lightweight and resistant to many forms of corrosion.

Disadvantages: Some plastics persist in the environment, can break into microplastics and are difficult to recycle if contaminated or mixed with other materials.

Exam tip: Do not assume every plastic has the same properties. The type of plastic and how it is manufactured affect its suitability.

15. Food preservation methods

Definition: Food preservation is the process of slowing or preventing spoilage so that food remains safe and usable for longer. Preservation methods work by controlling microorganisms, moisture, temperature or the conditions needed for spoilage.

Why food preservation is useful:

• Reduces food waste.

• Extends shelf life.

• Makes seasonal foods available later.

• Helps with storage and transport.

Important: Preservation does not automatically make spoiled food safe. Food must be prepared, processed and stored correctly.

Exam tip: Be able to match a preservation method to its principle, not only memorise the name.

16. Plastics: meaning, type and properties

Definition: A plastic is a material made from polymers that can be shaped during manufacturing. Plastics are commonly classified into thermoplastics and thermosetting plastics according to how they behave when heated.

Type 1: Thermoplastics

Thermoplastics soften when heated and harden when cooled, so they can often be reshaped several times. Examples include polyethylene (PE), polypropylene (PP) and PVC.

Properties of thermoplastics:

• Can often be reheated and reshaped.

• Many can be recycled if collected and processed correctly.

• Their flexibility, strength and heat resistance vary by type.

Type 2: Thermosetting plastics

Thermosetting plastics undergo a curing process that forms a rigid structure, so they cannot simply be melted and reshaped like thermoplastics. Examples include many epoxy resins and phenolic plastics.

Properties of thermosetting plastics:

• Often maintain their shape at higher temperatures than common thermoplastics.

• Can be hard and rigid.

• They cannot be remoulded by ordinary reheating once fully cured.

Exam tip: The main difference is what happens when the material is heated after it has been made.

17. Advantages of recycling plastics

Definition: Plastic recycling involves collecting and processing plastic waste so that the material can be used to make new products. It can reduce the amount of plastic sent to landfill and reduce demand for some newly manufactured plastic, depending on the material and recycling process.

Advantages:

• Reduces landfill waste: Less plastic may need to be buried in landfill sites.

• Conserves raw materials: Recycled plastic can replace some newly produced plastic.

• Can save energy: Some recycling processes use less energy than producing equivalent material from raw resources, although this varies.

• Can reduce litter: Effective collection and recycling systems can prevent plastic waste from entering the environment.

• Creates jobs: Collection, sorting, processing and manufacturing can provide employment.

• Supports reuse of resources: Waste plastic can become a useful input for another product.

Limitations:

• Plastic often needs to be sorted by type.

• Food and other contamination can make recycling harder.

• Not every plastic product is recyclable through every local system.

• Recycling does not eliminate all plastic pollution.

Exam tip: If asked for three advantages, give three different points and explain each one briefly. Do not write three versions of “it helps the environment.”

18. Hydraulics and pneumatics system

Definition: Hydraulic and pneumatic systems transmit energy through a fluid to operate a machine or mechanism. Hydraulics use a liquid, while pneumatics use compressed gas, usually air.

Hydraulic system sequence: A pump creates pressure in the liquid, the liquid transfers that pressure, and an actuator produces movement.

Pneumatic system sequence: A compressor supplies compressed air, a valve directs it, and an actuator converts the air pressure into movement.

Similarities:

• Both use a fluid to transmit energy.

• Both use valves and pipes or passages.

• Both can move or control machine parts.

• Both require suitable components and maintenance.

Exam tip: If asked which system is more suitable for lifting a very heavy load, hydraulics are often the better choice because liquids transmit pressure effectively and hydraulic systems can generate large forces.

19. Mechanical advantage of a system

Definition: Mechanical advantage (MA) describes how much a machine multiplies the input force. It compares the output force with the input force and shows whether a machine allows a smaller effort to produce a larger force.

Formula:

\boxed{MA=\frac{\text{Output force}}{\text{Input force}}}

Mechanical advantage has no unit because it is a ratio of two forces measured in the same unit.

Worked example:

A machine uses an input force of 25 N and produces an output force of 150 N.

MA=\frac{150}{25}=6

The mechanical advantage is 6. In this example, the output force is six times the input force.

Interpreting mechanical advantage:

• : The machine multiplies force.

• : The machine does not multiply force.

• : The output force is smaller than the input force, but the machine may provide other benefits, such as greater speed or distance.

For an ideal hydraulic system:

MA=\frac{A_{\text{out}}}{A_{\text{in}}}

For an ideal pulley system: The mechanical advantage is approximately the number of rope sections supporting the moving load.

Important: Real machines experience friction and other losses, so their actual mechanical advantage may be lower than the ideal value.

20. System diagram of a hydraulic jack

Definition: A system diagram represents the main parts of a device and shows how they connect or interact to achieve a purpose. A hydraulic jack diagram should show how the pump, valves and hydraulic fluid transfer pressure to the lifting ram.

Simplified hydraulic jack system:

Input: Handle operated by user

Pump piston

Pushes hydraulic fluid through a check valve

Hydraulic fluid under pressure

Pressure is transmitted through the liquid

Output ram / large piston

Moves upwards and lifts the load

Output: Load is raised

The release valve: Opening it allows the pressurised fluid to return to the reservoir, letting the ram lower in a controlled way.

Labels to include in an exam drawing:

• Handle

• Pump piston

• Hydraulic fluid

• Check valve

• Release valve

• Output ram or lifting piston

• Load

• Reservoir, if shown in the design

Exam tip: Arrows should show the direction of movement or fluid flow. A system diagram is meant to show how the parts work together, not necessarily every internal detail of a real jack.

21. Electric/electronic components (circuit diagram)

Definition: A circuit is a complete path through which electric current can flow from a power source and through connected components. Circuit diagrams use standard symbols to represent components, making circuits easier to understand without drawing the real components.

Main components:

Series circuit: Components are connected along one path, so the same current flows through each component.

Parallel circuit: Components are connected on separate branches, giving current more than one path.

Simple circuit layout:

      Switch       Ammeter     Resistor      Bulb

  ┌────o/ o─────────( A )──────[ R ]────────( X )──┐

  │                                               │

  └───────────────────| |────────────────────────┘

                      Cell

This is a simplified text drawing; use the standard circuit symbols taught in class when drawing your final exam diagram.

Voltmeter placement: To measure the potential difference across the resistor, draw the voltmeter on a separate branch connected to both ends of the resistor.

Exam tip: Remember this distinction: ammeter in series; voltmeter in parallel.

22. Preserving metals

Definition: Preserving metals means protecting them from corrosion, wear or other forms of damage so that they remain useful for longer. Iron and steel commonly rust when exposed to both oxygen and moisture, so protective methods reduce their exposure or make the surface more resistant.

Methods of preserving metals:

Why preserve metals?

• Extends the lifespan of metal products.

• Reduces repair and replacement costs.

• Helps maintain strength and appearance.

• Can improve safety by reducing corrosion-related damage.

Important distinction: Rust specifically refers to corrosion of iron and iron-containing materials; other metals may corrode in different ways.

Exam tip: If a question describes a metal object outdoors, explain how the chosen method protects it from moisture, oxygen or other corrosive conditions.

23. Ohm’s law

Definition: Ohm’s law states that, for a conductor under constant physical conditions, the current through it is directly proportional to the potential difference across it. The relationship between voltage, current and resistance is used to calculate an unknown electrical value.

Formula:

\boxed{V=I\times R}

Where:

• = voltage or potential difference, measured in volts (V)

• = current, measured in amperes (A)

• = resistance, measured in ohms (Ω)

Rearranged formulas:

I=\frac{V}{R}R=\frac{V}{I}

Worked example 1 — Calculate current:

Voltage = 12 V, resistance = 4 Ω.

I=\frac{12}{4}=3\text{ A}

The current is 3 A.

Worked example 2 — Calculate voltage:

Current = 2 A, resistance = 5 Ω.

V=2\times5=10\text{ V}

The voltage is 10 V.

Worked example 3 — Calculate resistance:

Voltage = 9 V, current = 3 A.

R=\frac{9}{3}=3\ \Omega

The resistance is 3 Ω.

Relationships to remember:

• At constant resistance, increasing voltage increases current.

• At constant voltage, increasing resistance decreases current.

Exam tip: Write the formula first, substitute the values, calculate and include the correct unit.

24. Logic gate

Definition: A logic gate is an electronic circuit that takes one or more binary inputs and produces a binary output. Binary values are represented by 0 and 1, commonly meaning OFF/LOW and ON/HIGH in school-level circuit questions.

AND gate: The output is 1 only when both inputs are 1.

OR gate: The output is 1 when at least one input is 1, including when both inputs are 1.

NOT gate: The output is the opposite of its single input; 0 becomes 1 and 1 becomes 0.

Truth table:

NOT gate truth table:

Examples in everyday systems:

• An AND condition could require two safety switches to be active before a machine operates.

• An OR condition could switch on an alarm if either of two sensors detects a problem.

• A NOT condition could turn on an indicator when a sensor signal is OFF, depending on the circuit design.

Exam tip: Do not confuse AND and OR. For AND, one missing 1 makes the output 0; for OR, a single input of 1 makes the output 1.

25. Resistor colour code

Definition: A resistor colour code uses coloured bands to show a resistor’s resistance value and tolerance. In a common four-band code, the first two bands give the first two digits, the third band gives the multiplier and the fourth band gives the tolerance.

Four-band resistor

Red

Violet

Brown

Gold

Example bands: red – violet – brown – gold

Colour digits

Multiplier and tolerance

Worked example

A resistor has the bands red – violet – brown – gold.

• Red = 2.

• Violet = 7.

• Brown multiplier = ×10.

• Gold tolerance = ±5%.

27\times10=270\ \Omega

Answer: 270 Ω ±5%.

Another example: brown – black – red – gold.

• Brown = 1; black = 0, giving 10.

• Red multiplier = ×100.

• , or 1 kΩ ±5%.

How to read the bands: Start at the end where the bands are grouped closer together. The tolerance band is often gold or silver and is separated slightly from the others.

Exam tip: Do not treat the third band as another digit. In the four-band system, it is the multiplier.

What to prioritise when revising

Based on your earlier diagnostic quiz, give extra practice to these topics because you previously made mistakes in them:

• Resistor colour code — reading the digits, multiplier and tolerance correctly.

• Logic gates — especially the difference between AND and OR.

• Circuit diagrams — ammeter in series and voltmeter in parallel.

• Load, force and moments — use force × perpendicular distance.

• Gears — calculate the number of turns using the teeth ratio.

• Hydraulics and mechanical advantage — use the correct area and force ratios.

• Recycling plastics — learn several distinct advantages and explain them.

These are priorities based on your first quiz, not a claim that the other topics are unimportant. Since your scope contains 25 topics, make sure you revise every section at least once before concentrating on the topics where you lose marks.