1. Pressure
1.1. Calculating pressure
1.1.1. Force/area
1.2. can increase and decrease
1.2.1. Increase:
1.2.1.1. force more, area same
1.2.1.2. force same, area less
1.2.2. Decrease:
1.2.2.1. force less, area same
1.2.2.2. force same, area more
1.3. High pressure: decrease area/increase force
1.3.1. examples:
1.3.1.1. Sharp knife [have smaller surface area, so when same force is used to cut something, higher pressure, allow us to cut easily]
1.3.1.2. High heels
1.3.1.3. Soccer shoes
1.3.1.4. Thumbtack
1.4. Low pressure: Increase area/decrease force
1.4.1. examples:
1.4.1.1. Camel
1.4.1.2. Skiing
1.4.1.3. Army truck/excavator
2. Forces
2.1. Push and pull
2.2. If there are two forces acting on opposite directions of an object and one is stronger than the other, the object will move in the direction of the stronger force.
2.3. Types of forces
2.3.1. Frictional
2.3.1.1. eg. if an object is pushed along a rough surface, there will be a larger frictional force acting in the opposite direction.
2.3.1.2. Useful
2.3.1.2.1. enable walking
2.3.1.2.2. light matchsticks
2.3.1.3. Negative
2.3.1.3.1. wear and tear
2.3.1.3.2. produce heat
2.3.1.3.3. Reduce efficiency of machines
2.3.1.4. How to reduce
2.3.1.4.1. lubricants
2.3.1.4.2. ball bearings
2.3.1.4.3. smoothen surface
2.3.1.4.4. Streamlining
2.3.2. Gravitational
2.3.2.1. An apple hanging from a shorter tree has less gravitational force acting on it than a similar apple hanging from a taller tree.
2.3.2.2. An apple that is heavier than another apple which is hanging from the same height will have more gravitational force acting on it.
2.3.3. Magnetic
2.3.3.1. Exerted by magnet on another magnet/magnetic material
2.3.3.2. Uses
2.3.3.2.1. fridge door
2.3.3.2.2. Ez-link card/ATM card
2.3.3.2.3. Junkyard
2.3.3.2.4. Magnetic door holder
2.3.3.2.5. Maglev train