1. FORCE
1.1. A push or a pull
1.2. SI Unit: Newton Symbol: N
1.3. Examples of FORCES
1.3.1. Frictional Force (Friction)
1.3.1.1. Advantages
1.3.1.1.1. There is friction between two moving objects when they are in contact with each other.
1.3.1.1.2. Slows down and/or stops a moving object
1.3.1.1.3. Produces heat
1.3.1.2. Disadvantages
1.3.1.2.1. Makes movemnt more difficult
1.3.1.2.2. Causes wear and tear
1.3.1.3. Ways to reduce friction
1.3.1.3.1. Using smooth surfaces
1.3.1.3.2. Lubrication
1.3.1.3.3. Ball bearings
1.3.1.3.4. Streamlining
1.3.2. Magnetic Force
1.3.2.1. A magnet can attract objects made of steel, iron, nickel and cobalt.
1.3.2.2. Forces between magnets
1.3.2.2.1. A magnet has 2 poles - North pole and South pole
1.3.2.2.2. Like poles repel (push) while unlike poles attract (pull).
1.3.3. Gravitational Force (Gravity)
1.3.3.1. Pulls objects to the center of the Earth.
1.3.3.2. Exists between any two objects.
1.3.4. Weight
1.3.4.1. The weight of an object depends on the force of gravity pulling on that object.
1.3.4.2. An object is heavier when the force of gravity pulling on it is greater.
1.3.4.3. Measured using a spring balance and it is measured in Newtons.
2. Effects of Forces
2.1. Change the shape or size of an object.
2.2. Move a stationary object or stop a moving object.
2.3. Change the speed of a moving object
2.4. Change the direction of a moving object.
3. How do we measure a force?
3.1. Force-meters
3.1.1. Spring balances
3.1.1.1. Extension spring balance
3.1.1.2. Compression spring balance
4. PRESSURE
4.1. The force exerted perpendicularly per unit area.
4.2. Depends on force and area.
4.3. Can be increased by reducing area.
4.4. Can be decreased by increasing area.
4.5. Calculating Pressure
4.5.1. Pressure = Force/Area
4.5.2. SI Unit: Pascal (Pa)
4.5.3. Sample Question: An elephant stands on one foot, and the lady stands on one stiletto heel, but the lady's heel exerts more pressure than the elephant's foot. Why is this so? Answer: The force exerted by the elephant's foot and the lady's stiletto heel is the same, but because the lady's stiletto heel is smaller than the elephant's foot, the surface area in contact with the lady's stiletto heel is smaller, hence the pressure exerted is higher.