# Pressure and Force

Get Started. It's Free Pressure and Force ## 17. Force

### 17.5. 3 Types of forces

17.5.1. Magnetic force

17.5.1.1. Magnetic force is a force exerted by a magnet on another magnet or on a magnetic material such as iron, steel, cobalt and nickel.

17.5.1.2. Unlike poles will attract while like poles repel each other.

17.5.1.3. We use magnetic force at the door of fridge, EZ Link, junk yard, magnetic door catch and magnetic train.

17.5.2. Gravitational force

17.5.2.1. Gravitational force (weight) is a force that causes objects to be attracted to the Earth due to gravity.

17.5.2.2. Examples of gravitational force are a coconut falling from tree and a ball being thrown up will come down.

17.5.3. Frictional force

17.5.3.1. To reduce friction, we need to use lubricants, ball bearing, or we smooth the surfaces by polishing the surface.

17.5.3.2. Friction also causes wear and tear and produces heat which is bad for an efficiency of the machine.

17.5.3.3. Friction enables us to walk and light matchstick

17.5.3.4. Friction slows down or stop moving things and produces heat.

17.5.3.5. Frictional force occurs when 2 moving surfaces are in contact

## 18. Pressure

### 18.3. The formula to calculate pressure

18.3.1. force/area

### 18.4. To increase pressure

18.4.1. increase force

18.4.2. decrease area

18.4.3. Examples

18.4.3.1. high heels

18.4.3.2. Sharp knife

18.4.3.2.1. It has a smaller surface area, so when we use the same force to cut something, a higher pressure will allow us to cut it easily.

### 18.5. To decrease pressure

18.5.1. increase area

18.5.2. decrease force

18.5.3. Examples

18.5.3.1. Army truck

18.5.3.2. Excavator

18.5.3.3. skiing

18.5.3.4. camel