# Forces and pressure

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Forces and pressure

## 1. Forces

### 1.1. What are forces?

1.1.1. a push or a pull

1.1.2. exerted when one thing interacts with another.

### 1.2. Examples of actions involving pushing or pulling

1.2.1. Lifting

1.2.2. Bending

1.2.3. Stretching

1.2.4. Twisting

1.2.5. Squeezing

### 1.3. Measuring force

1.3.1. force meter or Newton meter

### 1.4. Units of forces

1.4.1. SI unit: Newton

1.4.2. Symbol: N

1.4.3. Named after English scientist Sir Isaac Newton

### 1.5. Types of forces

1.5.1. Frictional force

1.5.1.1. How to reduce friction?

1.5.1.1.1. Using smooth surfaces

1.5.1.1.2. Using ball bearing

1.5.1.1.3. Lubrication

1.5.1.1.4. Streamlining

1.5.2. Magnetic force

1.5.2.1. What is magnetic force?

1.5.2.1.1. Force exerted by a magnet on a magnetic material or another magnet.

1.5.3. Gravitational force

1.5.3.1. What is gravitational force?

1.5.3.1.1. Also known as gravity

1.5.3.1.2. Exists between any two objects

1.5.3.1.3. This is the force that causes all objects to be attracted to the Earth.

1.5.3.2. Example of gravitational force

1.5.3.2.1. A coconut falling from the tree

1.5.3.2.2. A ball coming down after bring thrown skywards

## 3. Pressure

### 3.1. What is pressure?

3.1.1. Pressure is the force acting per unit area

3.1.2. pressure increases when: The force increases; or The area decreases

3.1.3. Pressure = Force / Area

3.1.4. New node

### 3.2. Example of increasing pressure by reducing area

3.2.1. cutting an object using a sharp knife

### 3.3. SI unit

3.3.1. N/m2

3.3.2. Pascal (Pa)

3.4.1. N/cm2

### 3.5. Example of pressure

3.5.1. An elephant weighs 40 000 N. It stands on one foot with an area of 1000 cm2.

3.5.1.1. Pressure = 40 000 / 1000 = 40 N/cm

### 3.6. SI unit

3.6.1. N/m2

3.6.2. Pascal (Pa)

3.7.1. N/cm2

### 3.8. Example of pressure

3.8.1. An elephant weighs 40 000 N. It stands on one foot with an area of 1000 cm2.

3.8.1.1. Pressure = 40 000 / 1000 = 40 N/cm2