# Chapter F1-Forces

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Chapter F1-Forces

## 4. Important forces around us

### 4.1. Frictional force

4.1.1. opposes the motion of an object

4.1.2. occur when 2 moving surfaces are in contact

4.1.3. Effects of frictional force

4.1.3.1. Negative

4.1.3.1.1. car tyres/shoes got worn out/wear and tear in machineries

4.1.3.2. Useful

4.1.3.2.1. enable us to walk/hold things

4.1.3.3. Effects: heat produce/cause wear and tear/slow down moving objects

4.1.4. Ways to reduce friction

4.1.4.1. lubricant

4.1.4.2. ball bearings/rollers

4.1.4.3. smoothen surfaces by polishing

4.1.4.4. streamlining

### 4.2. Gravitational force

4.2.1. a force thats pulls object to the Earth (GRAVITY)

4.2.2. gravitational force=weight

4.2.2.1. W=mg (gravitational field strength) [gEarth=10ms-2 = 10N/kg]

### 4.3. Magnetic force

4.3.1. Magnetic force is the attraction of a magnet

4.3.1.1. LIKE POLES REPEL WHILE UNLIKE POLES ATTRACT (ATTRACTION/REPULSION)

4.3.2. can act at a distance

4.3.3. force exerted by a magnet on another magnet or another magnetic material

4.3.3.1. Magnetic materials

4.3.3.1.1. steel

4.3.3.1.2. iron

4.3.3.1.3. cobalt

4.3.3.1.4. nickel

4.3.4. Magnetic forces

4.3.4.1. door of fridge

4.3.4.2. Maglev train

4.3.4.3. magnetic door catch

## 5. Pressure

### 5.2. Increasing pressure

5.2.1. increase force

5.2.2. decrease area

5.2.3. Uses of high pressure

5.2.3.1. knife

5.2.3.2. sharp nails

5.2.3.3. spikes on soccer shoes

### 5.3. Decreasing pressure

5.3.1. decrease force

5.3.2. increase area

5.3.3. Uses of low pressure

5.3.3.1. camel

5.3.3.2. skiing

### 5.5. Calculating pressure

5.5.1. divide the force by the area on which you applied the force

5.5.2. Eg.the force is 800N and the area is 10cm2,the pressure will then be 80N/cm2