1. Pressure
1.1. Is the force acting per unit area
1.2. Increases when
1.2.1. Force increases
1.2.2. Area decreases
1.2.2.1. Example: We are able to pierce a nail into a piece of wood but not our finger
1.2.2.1.1. Force remains the same
1.2.2.1.2. Area of the nail is smaller than or finger
1.2.2.1.3. Force acts on a small area (nail) to give high pressure. With the finger, the same amount of force is spread over a large area. Thus, pressure is lower.
1.3. Low pressure is needed when
1.3.1. Detail 1
1.3.2. a larger surface is in contact with the ground, the pressure exerted on the ground is lower, so people or machines can move without sinking
1.4. Calculating pressure
1.4.1. Item 1
1.4.2. Item 2
1.4.3. Item 3
1.4.4. 1m2 =100x100=10000cm2
2. Force
2.1. Measuring force
2.1.1. SI unit: Newton(N)
2.1.2. Use a spring balance to measure
2.1.2.1. Extention
2.1.2.1.1. Spring stretches when force is applied
2.1.2.1.2. Greater the force, the more the spring stretches
2.1.2.1.3. Spring stretches when force is applied
2.1.2.2. Compression
2.1.2.2.1. Compresses when force is applied
2.1.2.2.2. Greater the force, the more the spring compreses
2.1.2.3. Compression
2.2. Effects
2.2.1. Change shape and size of object
2.2.2. Stop or start a moving object
2.2.3. Change its direction
2.2.4. Change the speed of the object
2.3. Push or Pull
2.3.1. Bending
2.3.2. Lifting
2.3.3. Stretching
2.4. Type of forces
2.4.1. frictional force
2.4.1.1. Happens when 2 moving surfaces are in contact
2.4.1.2. Effects
2.4.1.2.1. Produce heat
2.4.1.2.2. Slows down and stop moving objects
2.4.1.2.3. Slows down and stop moving objects
2.4.1.2.4. Make movements difficult
2.4.1.3. How to ruduce?
2.4.1.3.1. Using smooth surface
2.4.1.3.2. Ball bearing
2.4.1.3.3. Lubricant
2.4.1.3.4. Streamlining
2.4.2. magnetic force
2.4.2.1. Exerted by a magnet on a magnetic material or another magnet
2.4.2.2. Bar magnets has 2 poles
2.4.2.2.1. North pole
2.4.2.2.2. South pole
2.4.2.3. Forces
2.4.2.3.1. Like poles repel
2.4.2.3.2. unlike poles attract
2.4.3. Gravitational force
2.4.3.1. Exist between any 2 objects
2.4.3.2. Causes objects to be attracted to earth
2.4.3.2.1. Coconut falling from tree
2.4.3.2.2. Ball coming down after being thrown upwars
2.5. weight
2.5.1. Gravitational force acting on object
2.5.2. Measured using spring balance in newtons
2.5.3. Greater the force of gravity pulling on the object, the greater the weight
2.5.3.1. Since force of gravity on earth is stronger than on the moon, we are heavier on earth than on the moon