# Structures and forces

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Structures and forces

## 1. Function

### 1.1. Function is what the structure does.

1.1.1. A structure like a house is made for people to live in.

1.1.2. An egg protects a chick from the environment. It is a shell structure because it is hollow.

## 2. Types of structures and form

### 2.1. Shell

2.1.1. A shell is hollow and has space inside. It's is also very light and can be strong. An example would be an egg.

2.1.1.1. A snail shell is a shell structure too.

### 2.2. Solid

2.2.1. A solid structure is a structure that is solid and uses mostly solid materials and are heavy. An example would be a Brick wall.

2.2.1.1. A stone bridge would be a solid structure too.

### 2.3. Combination

2.3.1. There are many types of structures from how they are buillt.They all are designed to do different things.

2.3.2. Combination structures are structures that combine the other types to make one. An example would be your body which has a frame and is solid.

2.3.2.1. Another one would be a stadium

### 2.4. Frame

2.4.1. Frame structures use many lines of materials to support each other and are lighter than solid structures.These structures can be very strong. An example would be Eiffel Tower which is made with frame of metal.

2.4.1.1. Another example would be a frame bridge

## 3. external forces or loads

### 3.1. External forces otherwise known as loads are forces that affects structures from the outside. An example would be wind which blows on many different structures.

3.1.1.1.1. Live loads are things inside.

3.1.1.1.2. Buildings are affected by gravity

### 3.2. External forces have magnitude,direction,point of application and plane of application.

3.2.1. Magnitude is how strong the force hit the object an example of low magnitude would be if someone blew on bubbles and strong would be a hurricane.

3.2.1.1. hurricane is stronger.

3.2.2. The direction of the force is which way it goes push or pull.

3.2.2.1. Pull

3.2.3. Point of application is where the force is applied and the plane of application is the angle it is applied at.

3.2.3.1. This is nail is being hit at almost 90 degrees and the force is applied at the top. The girl in the picture is pushing at the top.

## 4. Internal forces

### 4.1. Internal forces are materials acting between two parts of a body or a structure.

4.1.1. For example Tension, Compression, Torsion and Shear are four types of internal forces.

4.1.2. External forces can cause internal forces for example if you punch a wall the wall will compress.

4.1.3. Torsion is when an object twists like if I twist a towel to get the water out.

4.1.3.1. Towel is another example

4.1.3.1.1. Also when you do a rubiks cube you twist.

4.1.4. Shear is when parallel forces act in opposite directions.

4.1.4.1. when you rip something half it experiences shear.

4.1.5. Tension is when you pull in opposite ways.

4.1.5.1. The cables on two towers pull because of gravity. Another example is a tug a war match on the rope.

4.1.6. Compression is when you push one way.

4.1.6.1. If you punch someone their skin will become compressed.

4.1.6.1.1. Also when you sit on a chair.

## 5. Center of gravity

### 5.2. The centre of gravity of a human standing up is near their belly button and the centre of gravity of a truck is near the top.

5.2.1. Truck can have COG