1. Magnetic Force
1.1. Examples of magnetic forces in daily life
1.1.1. - A magnetic catch for the door of a cabinet keeps the door shut tight.
1.1.2. - The needle of a compass is a small magnet. A compass is used to give directions.
1.1.3. - The crane uses a powerful magnet to lift iron and steel objects.
1.2. A magnet can attract objects made of iron and steel. The magnet exerts a force called a magnetic force.
1.3. A magnet can also exert a force on other magnets. Bar magnets have two poles – a north-seeking pole (N) at one end and a south-seeking pole (S) at the other end.
1.4. When like poles face each other, the magnets repel (push).
1.5. When unlike poles face each other, the magnets attract (pull).
2. type(s) of forces
2.1. Gravitational Force
2.2. Magnetic Force
2.3. Frictional Force
3. Gravitational Force [a.k.a. Gravity]
3.1. It is the force that pulls the object towards the Earth.
3.2. The weight of an object depends on the force of gravity pulling on the object. The greater the force of gravity pulling an object, the heavier the object.
3.3. Gravity exists between any two objects (such as the Earth and a coconut or the Earth and a ball)
4. Frictional Force
4.1. Friction occurs whenever two moving surfaces are in contact with each other.
4.2. We cannot live without friction. Why?
4.2.1. [Nails]: Friction holds a nail in a wall.
4.2.2. [Bicycle]: Friction between the wheel and the brakes slows down the bicycle.
4.2.3. [Moving]: Friction between our feet and the ground gives us the grip needed to walk and run.
4.3. Friction slows down and stops a moving object.
4.4. Friction produces heat.
4.5. Friction can also be a problem.
4.5.1. Sometimes it can be a nuisance because it makes movement more difficult and wears away materials quickly.
4.5.1.1. Friction between the tyres and the road can wear out the rubber on the tyres.
4.5.1.1.1. It is dangerous on a wet road because the friction between the road and the tyre would then be very little, thus not being able to brake the car as quickly.
4.5.1.2. Friction between the air and the cyclist slows down the speed of the cyclist.
4.6. Ways of reducing friction
4.6.1. Use of lubricant (such as crude oil) to make the surface smoother
4.6.2. Use of ball bearings
4.6.3. Make the object more streamlined