# Force and Pressure

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Force and Pressure

## 3. Types of Forces:

### 3.1. - Gravitational force

3.1.1. - The weight of an object depends on the force of gravity pulling on that object, thus weight is the of gravitational force acting on an object.

3.1.1.1. - The greater the force of gravity pulling the object, the heavier the object will be, thus unlike your mass, your weight can change. Example, a person weighing 60kg on Earth, making her 600N, but on the Moon, her weight will only be 100N. This is becausethe gravitational pull of the Moon is about one six of Earth's, hence the person's weight differs.

3.1.2. - Gravity is the pulling force exerted on all objects on earth at all times and it can act from a distance. (e.g. Earth and a ball on the ground and Earth and a box on the table.)

### 3.2. - Frictional force

3.2.1. - Occurs whenever two moving surfaces are in contact.

3.2.2. - Produces heat e.g. When we rub our hands together, our hands feel hot.

3.2.3. - Can be useful as without friction, we would not be able to walk or run on the ground. (e.g. Friction between the wheel and the brakes slow down the bicycle)

3.2.4. - But friction also has disavantages as it causes wear and tear and opposes motion. (e.g. Friction slows down a cyclist due to air resistance and friction causes the tires of a car and the soles of our shoes to wear out.)

3.2.5. - There are ways to overcome friction:

3.2.5.1. - Having a stream-lined body shape. (e.g. Aeroplanes and fishes)

3.2.5.2. - Adding rollers

3.2.5.2.1. New node

3.2.5.3. - Lubrication

3.2.5.4. - Adding ball bearings

### 3.3. - Magnetic force

3.3.1. - Is a force exerted by magnets. Examples of magnetic materials are : Iron, Nickel, Steel and Cobalt.

3.3.2. - Magnets are used in objects like compasses or in catches for the door of a cabinet in order to keep the door of the cabinet shut and in Maglev trains.

3.3.2.1. The word "magev" comes from the words "magnetic levitation" (rising and floating). The magnets in the track and the train repel each other, lifting the train a few centimeters of the track. Since there is no contact between the track and the vehicle, friction is thus reduced and hence allows the train to travel very fast, up to 500km/h.

3.3.3. - A magnet is made out of north and South poles. Like poles repel while unlike poles attract.

3.3.4. - Can be applied from a distance.

## 4. Can be measured with

### 4.1. Force-meters

4.1.1. Extension spring balance

4.1.1.1. - Used by applying a force to pull the spring.

4.1.2. Compression spring balance

4.1.2.1. - Used when applying a force to compress it.