# Force and Pressure

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Force and Pressure

## 4. Types of forces

### 4.1. Frictional force

4.1.1. It is the force resisting two surfaces against each other.

4.1.2. It can be reduced.

4.1.2.1. Putting lubricant

4.1.2.2. Ball bearings

4.1.2.3. Rollers

4.1.2.4. Polishing

4.1.2.5. Streamlining

### 4.2. Magnetic force

4.2.1. A magnetized piece comes close to either a magnet or another magnetized piece.

4.2.2. Like poles attract

4.2.3. Unlike poles repel

4.2.4. Examples that use magnetic force

4.2.4.1. Fridge door

4.2.4.2. Maglev train

4.2.4.3. Magnetic door catch

## 6. Reducing pressure

### 6.1. Increase the surface area of an object.

6.1.1. Examples of objects that reduce pressure.

6.1.1.1. Skiing

6.1.1.2. Camels

6.1.1.3. Army truck

## 7. Uses of high pressure

### 7.1. Sharp knife

7.1.1. Blade has small area, so with the same force, it can produce high pressure.

### 7.2. Spikes on soccer shoes

7.2.1. It must have high pressure so they will sink into the ground and have better grip.

## 9. Calculating pressure

### 9.1. Formula for pressure

9.1.1. Pressure=Force/Area

### 9.2. Unit of pressure

9.2.1. pascal(Pa)