# Forces

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Forces

## 1. What?

### 1.1. a push or a pull

1.1.1. allows an object to move from one place to another

### 1.3. we cannot see forces

1.3.1. only see & feel their effects

## 4. Types

### 4.1. Elastic Spring

4.1.1. found in...

4.1.1.1. clothes peg

4.1.1.2. stapler

4.1.1.3. battery holder

4.1.1.4. pens

4.1.1.5. spring mattress

4.1.2. examples of obj

4.1.2.1. springs, rubber bands, bungee chords

4.1.2.2. spring balance

4.1.2.2.1. measure force neede to pull objects across table

4.1.3. what?

4.1.3.1. materials/obj that change shape when force is applied

4.1.3.2. returns to original shape when force is removed

4.1.3.2.1. But there is a limit

4.1.4. how?

4.1.4.1. pull

4.1.4.1.1. stretches

4.1.4.2. push

4.1.4.2.1. compress

### 4.2. Gravity

4.2.1. what?

4.2.1.1. pulls everything down to earth

4.2.1.2. force that acts at a distance

4.2.2. water flows downwards

4.2.3. effects?

4.2.3.1. increases speed when going downslope

4.2.3.2. makes things in the air fall down

4.2.3.3. BUT!

4.2.3.3.1. further obj from earth = lesser pull of gravity

4.2.3.4. WEIGHT

4.2.3.4.1. all obj on earth has weight

4.2.3.4.2. gravitational force between object and Earth

4.2.4. uses?

4.2.4.1. refrigerator doors

4.2.4.2. magnetic buttons

4.2.4.3. 'MagLev' trains

4.2.5. what?

4.2.5.1. force that acts at a distance

4.2.5.2. pushing and pulling actions of magnets

### 4.3. Magnetic

4.3.1. effects?

4.3.1.1. attracts magnetic materials

### 4.4. Friction

4.4.1. what?

4.4.1.1. when 2 surfaces rub together

4.4.1.2. opposes motion

4.4.1.2.1. acts opposite of direction of moving obj

4.4.1.3. produces heat

4.4.2. pros

4.4.2.1. grip

4.4.2.1.1. tyres, shoes

4.4.3. cons

4.4.3.1. obj move slowly

4.4.3.2. overheat

4.4.3.3. wear out

4.4.4. solutions

4.4.4.1. lubricants

4.4.4.2. rollers & wheels

4.4.4.3. ball bearings

4.4.4.4. hovercrafts

4.4.4.4.1. air cushion

4.4.5. when else is friction useful/useless?

## 5. Effects of forces

### 5.1. obj starts moving

5.1.1. faster

5.1.2. slower

5.1.3. change direction

5.1.4. stop moving