Grade 8 Technology - Exam Study Notes (Units 3, 6, and 7)

Graphical communication

The use of sketches, plans, symbols, and technical drawings to communicate design ideas accurately.

Working drawing

A precise drawing with measurements and details used to make an object.

Sketch

A quick freehand representation of an object or design idea.

Visible outlines

Thick continuous lines used in drawings to show external edges.

Construction/projection lines

Thin continuous lines used to construct shapes and align features between views.

Hidden details

Short dashed lines used to represent features not visible from a specific view.

Centre lines

Long-short dashed lines used to indicate axes of symmetry or centers of holes and circles.

Dimension lines

Thin lines with arrowheads used to indicate sizes and measurements on technical drawings.

Scale

A ratio comparing the drawing size with actual size, such as $1:1$ (full size), $1:2$ (half size), or $2:1$ (twice actual size).

Isometric drawing

A three-dimensional view constructed with vertical lines and two sets of lines drawn at $30^\text{o}$ to the horizontal, keeping parallel edges parallel.

Orthographic drawing

A method of technical drawing showing separate front, top, and side views drawn to scale, with corresponding edges aligned using projection lines.

First-angle orthographic layout

A drawing layout where the top view is placed below the front view, and the left-side view is placed to the right of the front view.

Perspective drawing

A drawing technique that creates depth using a horizon line and one or two vanishing points.

Station point (SP)

The exact position of the viewer in a perspective drawing.

Machine

A device that makes work easier by changing the size or direction of a force or motion.

Mechanism

A set of moving parts that transfer or change force or motion.

Effort

The applied force used to operate a mechanism or machine.

Load

The force or weight being moved by a mechanism or machine.

Fulcrum

The fixed pivot point around which a lever rotates.

First-class lever

A lever where the fulcrum is situated between the effort and the load (e.g., seesaw, scissors).

Second-class lever

A lever where the load is situated between the fulcrum and the effort (e.g., wheelbarrow).

Third-class lever

A lever where the effort is applied between the fulcrum and the load (e.g., tweezers, human forearm).

Mechanical advantage (MA)

The ratio of load to effort ($\text{MA} = \frac{\text{Load}}{\text{Effort}}$), or for an ideal lever, the effort-arm length divided by the load-arm length.

Spur gears

Toothed wheels mounted on parallel shafts; two meshing external spur gears rotate in opposite directions.

Idler gear

A gear positioned between the driver and driven gear that changes the direction of rotation without altering the overall gear ratio of a simple gear train.

Bevel gears

Toothed gears that transfer rotational motion between intersecting