Forces and Structures

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Forces and Structures

1. Forces

1.1. External Forces

1.1.1. Any force that acts on a structure from the outside, either with contact or non-contact.

1.1.1.1. Gravity

1.1.1.1.1. Gravity is the natural attracting force between 2 objects.

1.1.1.2. Winds

1.1.1.2.1. Winds are air currents caused by a difference in air pressure.

1.1.1.3. Water

1.2. Internal forces

1.2.1. Forces that acts on a stucture from the inside, from different parts of the structure.

1.2.1.1. Compression

1.2.1.1.1. pushing 2 parts/different structures together, reducing their volume.

1.2.1.2. Tension

1.2.1.2.1. Stretching an object longer, keeps structures stretched tight.

1.2.1.3. Torsion

1.2.1.3.1. Twisting an object, usually in opposite directions on 2 ends.

1.3. Magnitude

1.3.1. How strong or a weak a force is

1.3.1.1. Strong forces are usually destructive, and they cause huge amounts of damage.

1.3.1.1.1. Tornadoes can spin at incredible speeds, sometimes over 480 kilometers per hour, and they can easily destrying buildings and cars.

1.3.1.2. Direction

1.3.1.2.1. The path of a force, with some usual directions being up, down, left, right, forward, and backward.

1.3.1.3. Weak forces, on the other hand, can't interfere with anything that is heavier or stronger.

1.3.1.3.1. A light wind, a breeze, is only enough to bend flowers.

1.4. Strength

1.4.1. Strength is how strong a structure or material is, or how much force can it take before failure.

1.4.1.1. A steel beam would obviously be stronger than a wooden plank.

1.4.1.2. However, if the steel beam is worn and rusted while the wood plank is brand new and reinforced, the wooden plank should be stronger.

2. Stability

2.1.1.1.1. The combined weight of a structure itself and other immovable objects acting on the structure. A force increasing or decreasing over a long period of time is also considered a static load.

2.1.2.1.1. An inconstant, changing force acting on a structure, possibly with a changing point of application and changing magnitude too.

2.3. The balance point on an object, where the mass is concentrated and balanced. The object would not topple if supported at this point.

2.3.1. A seesaw with 2 people of the same weight sitting on the 2 opposite chairs.

2.3.2. A bus tilted 30 degrees may not tile over, but if its tilted 60 degrees it will topple.

2.4. Plane and point of application

2.4.1. Point of application: The location/exact point where the force is applied

2.4.1.1. If you twisted the doorknob of a door, the doorknob would be the point of application.

2.4.1.2. If you pushed the door instead, the point where your hand touched the door would be the point of application.

2.4.2. Plane of application: An imaginary flat surface where the applied forces pass though.

2.4.2.1. If the doorknob was at 2/3 of the door, the plane of application would be at 2/3 of the door horizontally.

2.4.2.2. If you pushed door straight horizontally, then the plane of application would go horizontally though the door with the starting side where you touched the door.

3. Structures

3.1. Shell structures are strong, lightweight structures that are usually hollow and curved.

3.1.1. Eggs are great shell structures, are they can withstand incredible amounts of force.

3.1.2. Domed stadiums also use curves to withstand the pull of gravity of a huge celing.

3.2. Frame structures are structures fastened together by multiple parts.

3.2.1. The Eiffel Tower is definitely one of the most famous structures on the world, and it's frame design is a technological marvel.

3.2.2. Climbing domes for kids are also very strong, and one can support multiple kids at the same time.

3.3. Solid structures are structures with no or nearly no hollows in it, making it heaviest and the strongest with compared to shell and frame structures of the same volume.

3.3.1. The Pyramids are nearly fully solid, but they do have rooms within them.

3.3.2. Mountains are solid structures too, but many of them may have caves inside.

3.3.3. Or much thinner and recent structures like the Washionton Monument.

3.4. Combination structures are structures that combines properties of all 3 types of structures.

3.4.1. Houses and most man-made buildings are combination structures, since they have frames to start, uses shells to support, and covers the outside with solids like bricks.

3.4.1.1. For example, the Sydney Opera House.

3.4.1.2. Or just an average house that most people live in.

3.4.2. Bridges are also combination structures, since they use ties and struts (frames) to support them, solids as the road surface, and arches (shell) beneath.

3.4.2.1. Like the Golden Gate Bridge,

3.4.2.2. Or older bridges built by our ancestors.

3.5. Form

3.5.1. The shape/visual apperance of a structure

3.5.1.1. A mountain may appear to be covered with forests and snow or grass.

3.5.1.2. A dam would have concrete and steel beams on the outside.

4. Functions

4.1. An purpose a structure is designed to fulfill/An objective the structure is designed to do

4.1.1. For example, bridges are designed to span gaps.

4.1.2. Houses are designed to accomedate people.

4.1.3. Some structures, like dams, can have multiple functions. For example, they can generate electricity, prevent flooding, and cut off invasive species.