1. We cannot see forces, but we can see the effects of forces.
1.1. Force can can the speed of a moving object.
1.2. Change the shape and size of an object.
1.3. Force can change the direction of a moving object.
1.4. Force can start moving a stationary object.
1.5. Force can stop moving a moving object.
2. Force is a push or pull.
2.1. An example is pushing close a door.
2.2. Another example is pulling a box towards you.
3. We measure force using force meters: Spring Balance.
3.1. Compression spring balance.
3.1.1. The spring gets compressed when a force acts upon it.
3.2. Extension spring balance.
3.2.1. The string stretches a force pulls on it. The greater the force, the more the spring stretches.
4. S1 unit for force: Newton (N)
5. Pressure is the amount of force exerted perpendicular per unit area.
5.1. Air pressure
5.2. Water pressure
6. S1 unit area for pressure: Pascal (Pa)
7. Formula for calculating pressure: Force divided by area.
8. To increase pressure.
8.1. on a solid, pus harder onto it.
8.2. on a liquid, push harder onto it.
8.3. on a gas, either increase the amount of gas, the temperature, or decrease the volume of the container.
9. To decrease pressure.
9.1. Decrease the amount of force applied to the object.
9.2. Increase the area.
10. If the unit of area is square centimeters (cm2), the unit of pressure will be Newton per square centimeter (N/cm2)
11. 1Pa = 1N/m2
12. Different types of forces
12.1. Frictional force
12.1.1. Created whenever 2 surfaces move or try to move across each other.
12.1.2. Opposes motion
12.1.3. Depends on the texture of both surfaces, and on the amount of contact force pushing the 2 surfaces together.
12.1.4. Reduced by oil, grease.
12.1.5. Can be useful or harmful
12.1.5.1. Harmful: when 2 rough surfaces rub each other, the friction is great and friction produces heat, so there is a large amount of heat produced and a fire or explosion may start.
12.1.5.2. Useful: Intentionally apply frictional force to make transportation safer and more controllable.
12.2. Magnetic Force
12.2.1. Highest at 2 ends of the magnet.
12.2.2. Causes attraction and repulsion; like poles repel and unlike poles attract.
12.2.3. Non-metallic materials are not magnetic materials.
12.2.4. Some of the metallic materials are magnetic but some are not.
12.2.4.1. Magnetic: Steel, Iron, Nickel, Cobalt
12.2.4.2. Non-magnetic: aluminium, copper
12.3. Gravitational force
12.3.1. Not a force of contact
12.3.2. Is the force of attraction between all masses in the universe
12.3.3. Any object on the Earth/ close to the Earth will experience gravitational force
12.3.4. The gravitational force on the Earth is the force the Earth exerts on you.
12.3.5. Can be good or bad
12.3.5.1. Good: It keeps us on the ground
12.3.5.2. If there is a hole, we would fall into it.