Form and Function: Unit Review

(a) solid, (b) frame, (c) shell.

A skeleton of joined parts (beams, columns, braces).

Advantage: light, uses little material, encloses a big space. Disadvantage: can crack if a force hits one small spot; hard to repair.

Foundation: solid. Studs: frame.

The dome spreads the load so the snow blocks are squeezed together; it can be built from snow alone, sheds wind and keeps warmth in.

Decide the job first, then choose the shape and build that does it well.

About 59 N (6 × 9.8 = 58.8), down, at the middle, on the shelf's top surface.

The billboard's front face.

The plane of application changed; on its edge the ruler is tall in the direction of the load, so it resists bending.

Live load.

80 ÷ 20 = 4 cm.

It splits the square into two triangles, which can't change shape.

Strong supports (abutments), because an arch pushes outward at its feet.

The point where all of an object's weight seems to act; its balance point.

In the empty centre (the hole).

Hang it from two different holes with a plumb line, trace each line, and find where they cross.

When the line straight down from its CG falls outside its base.

Any two: a heavier base (lower CG), a wider base, anchor it.

To keep the combined CG over its base when it lifts a load.

Rotational symmetry.

Matching parts share the load equally, and the CG stays in the middle.

It is anchored into the building, which acts like a counterweight.

Any four: properties, cost, availability, ease of manufacturing, safety, appearance, environmental impact.

Concrete is weak in tension; steel is strong in tension.

It is light and resists rusting.

Any four: design errors, poor materials, poor construction, overloading, foundation problems, natural forces, aging and poor maintenance.

Weakening from a load put on and taken off many times.

The bridge was much heavier than designers calculated, and compression parts buckled.

25 × 3 = 75 kg.

Assess: inspections, tests, computer models. Improve: safety factor, building code, retrofit, load limits. Maintain: painting steel, sealing concrete, replacing worn parts, clearing snow.

It is not more than 2 but more than 1, so it logs "WATCH".

Health, safety and efficiency.

Any two: screen at or a little below eye level; wrists straight; feet flat; back supported; take breaks; good lighting.

4 ÷ 40 = 10%: yes.

(a) social, (b) environmental, (c) economic.

Giving up some of one thing to get more of another.

Their rights may be affected (governments have a duty to consult), and their knowledge of the land and water can improve designs.

1 400 ÷ 35 = 40.

A criterion (something the design must do).

Tension. Add more paper layers or a tape strip along the bottom.