1. What is a force?
1.1. It is a force or a pull.
2. What are the effects of forces?
2.1. Change the speed of a moving object
2.1.1. By increasing
2.1.2. By decreasing
2.2. Change the shape or size of an object
2.3. Start or stop a moving object
2.4. Change the direction of a moving object
3. How to measure force?
3.1. By using force meters which is a spring balance.
3.1.1. Types of spring balance
3.1.1.1. Extension spring balance
3.1.1.2. Compression spring balance
4. Important forces around us?
4.1. Frictional force
4.1.1. occurs whenever two moving surfaces are in contact. It slows down and stops a moving object. It also produces heat.
4.1.2. It is often a nuisance because it makes movement more difficult and wears away materials.
4.1.3. Ways of reducing friction: -Having a streamline shape -Oil on moving parts -Having smooth surface -Use of ball bearings
4.2. Magnetic force
4.2.1. A magnet can attract objects made of iron and steel. The magnet exerts a force called a magnetic force.
4.2.2. Examples of magnetic forces in daily life: -Needle in a compass -Magnetic catch for the door to keep the door shut -In a crane that use a powerful magnet to lift iron and steel objects.
4.3. Gravitational force
4.3.1. Gravitational force is a force that pulls the objects towards the Earth. Gravity exists between any two objects.
4.3.2. Weight
4.3.2.1. The weight of an object depends on the force of gravity pulling on that object.
4.3.2.2. The greater the force of gravity pulling an object, the heavier the object.
5. Pressure
5.1. Is the force per unit area applied in direction perpendicular to the surface of an object.
5.2. Pressure = force/area
5.3. Si unit is Pa = 1N/m2
5.4. How to increase pressure?
5.4.1. Pressure increases when the force increases or the area decreases.
5.4.1.1. How? - For the same force, when a smaller surface is in contact with an object, the pressure exerted is higher.
5.5. How to decrease pressure?
5.5.1. Pressure decreases when area increases or the force decreases.
5.5.1.1. How? - Low pressure are needed when people or machines move on soft ground or snow. When 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.
5.6. Examples of how pressure is used to move stuff on soft ground
5.6.1. Large surface area of the skis prevents the skier from sinking into the snow
5.6.2. Camel has large, flat feet to spread its weight over a large area. Camel does not sink because pressure is low
5.7. How to calculate pressure?
5.7.1. If the unit of area is square metres (m2), then the unit of pressure is newton per square metre (N/m2) since pressure is equal to force/area. This unit can also be called pascal (Pa) where 1 Pa = 1 N/m2. The pascal is the S1 unit for pressure!