# Structures and Forces

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Structures and Forces

## 1. Types of structures

### 1.1. solid

1.1.1. a solid structure is solid all the way through and is made of the same material

1.1.1.1. apple

1.1.1.2. mountain

1.1.1.3. tree

### 1.2. shell

1.2.1. a shell structure is hollow inside and is useful for storing items

1.2.1.1. igloo

1.2.1.2. dome

1.2.1.3. egg

### 1.3. frame

1.3.1. a frame structure is made of many different parts to create it

1.3.1.1. airplane

1.3.1.2. chair

1.3.1.3. table

### 1.4. combination

1.4.1. a combination structure is a structure that has many characteristics of 2 or more types of structures

1.4.1.1. house

1.4.1.2. human skeleton

1.4.1.3. car

## 2. external forces

### 2.1. a force applied to a structure from the outside of it

2.1.1. gravity

2.1.1.1. the force that pulls on all objects

2.1.1.1.1. the apple that fell on newton's head was being pulled down by gravity

2.1.1.1.2. the bridgre needs to support its own weight being pulled by gravity or else it will collapse

2.1.1.1.3. without gravity, this man would float inn midair

2.1.2.1.1. the weight when the structure supports itself

2.1.2.2.1. the load of which the structure has to support(this can be anything)

## 3. internal forces

### 3.1. an internal force is a force that are made by one part of a structure that affects other parts of the structures

3.1.1. compression

3.1.1.1. a force that makes something squished or pressed together

3.1.1.1.1. the person is compressing the chair by sitting on it

3.1.1.1.2. when the apple lands on newton's head, it creates compression

3.1.2. tension

3.1.2.1. a force that stretches somrthing to make it longer or wider

3.1.2.1.1. stretching makes your muscles feel tension

3.1.2.1.2. the elastic band stretching creates tension inside of the elastic band

3.1.3. shear

3.1.3.1. a force that pushes things to go in 2 opposite directions

3.1.3.1.1. tectonic plates shifting creates shear between the plates

3.1.4. torsion

3.1.4.1. a force that twists something

3.1.4.1.1. figure skaters spinning their bodies create torsion inside of them

3.1.4.1.2. in a tug of war, the rope experiences tension inside of it. if too much tension is made then the rope will break.

## 4. stability

### 4.1. the stability of a structure depends on...

4.1.1. the centre of grravity

4.1.1.1. the centre of gravity is determined from where most of the weight is

4.1.1.1.1. the giraffe's centre of gravity is where its neck and its body connects when it eats

4.1.1.1.2. a human's centre of gravity is his/her stomach area

4.1.1.1.3. a bed's centre of gravity is in the middle because there is almost no weight difference throughout the bed

4.1.2. the size of the base

4.1.2.1. the wider the base, the more stable the structure

4.1.2.1.1. a giraffe drinking water ahs its legs spread out wide to mmake a wide base

4.1.2.1.2. the triangle is the strongest shape and it has a wide base tomake it stable

4.1.2.1.3. a triangle on its corner is not very stable because the base is very small

4.1.3. the material it's constructed from

4.1.3.1. heavier materials like wood or steel are less likely to be pushed down

4.1.3.1.1. a house made of wood wouldn't be as strong as a house made of bricks

4.1.3.1.2. see picture above

## 5. applying forces

### 5.1. magnitude

5.1.1. the speed of the force

5.1.1.1. A strong gust would have a high magnitude.

5.1.1.2. A gentle breeze would have a low magnitude

5.1.1.3. A wrecking ball would have an extremely high magnitude.

### 5.2. direction

5.2.1. the direction of the force

5.2.1.1. The magnets would repel or pull towards eachother.

5.2.1.2. The force of gravity pulls down.

### 5.3. Point of application

5.3.1. where the force meets the structure

5.3.1.1. The point of application for the meteor on the Earth is the Atlantic Ocean

5.3.1.2. The point of application for the person is the centre of the door.

### 5.4. plane of application

5.4.1. the side of the structure the force hits

5.4.1.1. Wherever you kick the soccer ball is where the ball will aim.

5.4.1.2. Slapping someone in the face is applying force to the cheek (side) of someones face