Strength & Stability The Shapes of Objects pyramid • pyramids in Egypt • Sunway Pyramid

cone • party hat; ice-cream cone, traffic cone • Twin Towers

cuboid • cereal box, book • Parliament Building

cube • dice; rubik's cube • Kaabah

sphere • balls; marbles • Fuji TV Building Tokyo, Japan

hemisphere • igloo; helmet • National Science Centre

cylinder • tin can • Komtar Tower at Penang

Factors that Affect the Strength of a Structure o types of material used - objects that are made of steel and concrete are stronger than objects that are made of wood or glass. E.g. a concrete bench is stronger than a wooden bench

o how the object is placed - the manner in which bricks are arranged in a wall is obviously of great importance to the appearance and strength thereof

o shape of the structure - some shapes of construction are stronger.

To determine how the shape of a material can make it stronger. A flat piece of paper is not very strong, but when it is folded in an accordion shape, it becomes stronger and can support more weight. For example, corrugated cardboard, which has a layer of grooves and ridges, is much stronger than flat cardboard.

Factors that Affect the Stability of a Structure o base area - the bigger the base area, the more stable the object is. In other words, when the size of a model increases, the stability of the model also increases.

Example 1 Table A has a bigger base area than Table B. Table A is more stable than Table B.

Example 2 Cork (a) has a smaller base area than Cork (b). Cork (a) is less stable than Cork (b).

Example 3 Car RES 12 has a smaller base area than Car RES 10. Car RES 12 is less stable than Car RES 10.

Example 4 Models Q and R made from different number of rolls of papers that glued together. The papers are the same type. Both the models were blown using a fan with the same speed. Model Q fall. Model R still stand because it has the bigger base area and more stable.

o height - the higher the object, the less stable the object is. In other words, when the height of an object increases, the stability of the object decreases.

Example 1 Stool A is more stable than Stool B because it is shorter i.e. with a lower centre of gravity.

Example 2 Vehicle (a) is more stable than vehicle (b) because it is shorter.

o shape - taper the structure (make the top skinny and the base wide) Example 1 A pyramid is more stable than a cuboid of the same height and base area. Example 2 A cylinder is less stable than a cone of the same height and base area.

Example 3 The Eiffel Tower tapers from its base to the tip of the tower and is very similar to the geometric shape of a four sided pyramid.