1. forces
1.1. forces are not visible but the effects are
1.2. forces can be measured with force meters.spring balance are force meters.there are two type of spring balances extension spring balances and compression spring balances
1.3. frictional force
1.3.1. there is frictional force when two things are in contact
1.3.1.1. example:friction between the wheel and the brake slows down the bicycle
1.4. magnetic force
1.4.1. a force which can act from a distance using magnets with magnets or magnets with magnetic materials like steel etc
1.4.1.1. example: a magnetic catch for the door keeps the door shut tight
1.5. gravitaional force
1.5.1. a force that pulls the objects towards earth
1.5.1.1. example:we cant fly
2. moments
2.1. also known as turning effects of forces
2.2. moment of force depends on two factors
2.2.1. the size of the force
2.2.1.1. a greater force increases the moment
2.2.2. the perpendicular distance of the force from the turning point called the fulcrum
2.2.2.1. a larger distance also increases the moment
2.3. calculating moment
2.3.1. force x perpendicular distance of the force to the fulcrum
2.3.1.1. NM=n x m
2.3.1.1.1. newton-metre=newtons x metre