# The Science of Structures and Forces

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The Science of Structures and Forces

## 1. Forces

### 1.2. Internal Forces

1.2.1. Internal forces are forces that affects the whole structure from the inside.

1.2.2. Tension

1.2.2.1. One of the four internal forces. It stretches a structure apart, or lengthens it.

1.2.2.1.1. One example for tension, is when you stretch a rubber band.

1.2.2.1.2. Another example is a game of tug-of-war. Two people pull apart a rope. Tension is when you pull the rope apart.

1.2.3. Torsion

1.2.3.1. One of the four internal forces. It is the twisting of a structure.

1.2.3.1.1. One example is when you twist the water out of a towel.

1.2.3.1.2. When you twist the ruler between your hands.

1.2.4. Shear

1.2.4.1. One of the four internal forces. It is the pushing of a structure in opposite directions.

1.2.4.1.1. When you rub your hands together when you are cold.

1.2.4.1.2. When you rip a piece of paper in half, it will experience shear.

1.2.5. Compression

1.2.5.1. One of the four internal forces. It squeezes a structure together.

1.2.5.1.1. One example is when you sit on your bed. The springs in your mattress are pushed down.

1.2.5.1.2. Another example is when you squeeze the water of a sponge. You press the sponge together, which causes compression.

### 1.3. External Forces

1.3.1. External forces are forces that affect a structure from the outside.

1.3.1.1. Weather is example of a force that can push or pull a structure apart from the outside.

1.3.2. Gravity

1.3.2.1. Gravity is a normal force that brings to objects together.

1.3.2.1.1. An apple falling from it's tree. It cause by gravity pulling it down.

1.3.2.1.2. A river moves down hill because gravity brings it down.

2.1.2.1.1. For example, a house is a dead load because it cannot be moved. It has to support live loads, like people and furniture.

2.1.2.1.2. Another example is an elevator. It can't be moved and it has to support live loads like people, strollers and other weights.

2.1.3.1. Live loads are loads that can remove themselves from a structure.

2.1.3.1.1. An example of a live load is something sitting on a chair.

2.1.3.1.2. Another example of a live load is a person going up or down an elevator.

2.2.1. Dynamic loads are forces that are natural occurring events like weather that put force of a structure.

2.2.1.1. An example of a dynamic load is snow snowing on the roof of a building.

2.2.1.2. Another example of a dynamic load is rain raining on the roof of a building.

## 3. Structures

### 3.2. Frame Structures

3.2.1. A frame structure is made of many parts jointed together.

3.2.1.1. A bicycle is a frame structure since it is made of many parts joined together.

3.2.1.2. A skeleton is a frame structure because it is many parts linked with joints.

### 3.3. Solid Structures

3.3.1. A solid structure is not empty, but solid or almost.

3.3.1.1. A mountain is a solid structure because it is mostly made of solid rock and is not hollow.

3.3.1.2. A apple is a solid structure because it is not hollow.

### 3.4. Combination Structures

3.4.1. A combination structure is made up of two or more structures.

3.4.1.1. A house is combination structure because it is made up of a frame and solid structure.

3.4.1.2. A tent is a combination structure and is made of a frame and shell structure.

### 3.5. Shell Structures

3.5.1. A shell structure is hollow on the inside.

3.5.1.1. A egg is a shell structure since is is hollow in the inside.

3.5.1.2. A can is a shell structure since it is hollow in the inside.

## 4. Designing Structures

### 4.1. Form

4.1.1. The shape or mold a structure has or takes.

4.1.1.1. A cup has looks like a U shape because it's used for containing liquid.

4.1.1.2. A bed is big long, so we can rest on it.

### 4.2. Function

4.2.1. A given purpose to a structure or object.

4.2.1.1. The function for a bed is a place to rest or sleep when you are tired.

4.2.1.2. The function of a cup is to contain a drink, but it can also contain other things, like cereal.

### 4.3. The Strength of a Structure

4.3.1. The amount of force a structure can withstand.

4.3.1.1. Card stock paper is harder to rip than paper because card stock is stronger and can withstand more shear.

4.3.1.2. A bridge that is made without trusses will be weaker than a bridge with trusses.

### 4.4. Centre of Gravity

4.4.1. The part of a structure or object where the most weight acts on it from gravity.

4.4.1.1. The lower the centre of gravity on a tower, the more balance it has.

4.4.1.2. Giving a structure a big/heavy base will lower your centre of gravity.

## 5. Applying Force

### 5.1. Point of Application

5.1.1. The side where the force is directed at a structure.

5.1.1.1. For example, which would be more deadly? A head on collision for cars or a side collision.

5.1.1.2. If I wanted to hammer a nail, I should hit the side where the head is.

### 5.2. Plane of Application

5.2.1. The specific point where the force hits the structure.