Forces

1. frictional force

1.1. useful for brakes, nails and a runner

1.2. problem, worn out tyres, slows down a cyclist

1.3. ways to reduce friction

1.3.1. smooth surface

1.3.2. ball bearings

1.3.3. kuvricants

1.3.4. stream-lined shape

2. magnetic force

2.1. a magnet attracts objects made of iron and steel

2.2. like poles of a magnet repel

2.3. unlike poles of a magnet attract

2.4. example: maglev train, but it still encounters air resistance. As there is no friction between the train and the track, the train will go faster

3. gravitational force

3.1. it is a force which pulls objects towards the earth also known as gravity

3.2. weight

3.2.1. it is a force of gravity pulling on the object so the unit is Newton(N)

4. effects of forces

4.1. stop a moving object

4.2. slow down a moving object

4.3. change the shape or size of an object

4.4. change the direction of a moving object

4.5. start an object moving

5. how to measure a force

5.1. force meters

5.1.1. compression spring balance

5.1.2. extension spring balance