Force is a vector quantity. 

This means that it has its full
effect in a particular direction but that it also has reduced
effects in other directions. 



The effect of a force in a direction not along its own line of action is called a component of the force. 



The process of finding the magnitudes of the components of a force is called
resolving the force into its components. 






The force, F, in this diagram can be considered
to be the sum of two perpendicular forces, as shown in the next diagram. 



Imagine that these diagrams have been drawn to scale.


For
example, let 1cm represent 0.1N
of force. 












These forces are the vertical and horizontal components of F. 



From the diagram we see that the magnitude of the vertical component F_{v}
is given by 



and the magnitude of the vertical component F_{h} is given by 





The magnitude of the component of a force in a direction at 90° to its own
line of action is therefore always equal to zero. 

This is why it is often useful to resolve a force
into its vertical and horizontal
components: these two components can then be considered as two
independent forces. 
