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234 Chapter Nine
Example 9.1: Brushing Teeth
If we use a toothbrush correctly, and our teeth get cleaned properly, then we call
this brush action a normal useful action. We can illustrate this by the following
functional analysis diagram:
Brush
Toothbrush Teeth
mech.
However, if we use the toothbrush too gently and do not brush long enough, or
we use a worn toothbrush, then our teeth will not get enough cleaning. In this
case, we can use the following functional analysis diagram:
Brush
Toothbrush Teeth
mech.
Clearly, this is a case of an insufficient useful action.
If we use a very strong toothbrush and brush our teeth with much force and big
strokes, then our gums will get hurt, and so will our teeth. We can use the
following functional analysis diagram to describe this situation:
Brush
Toothbrush Teeth
Wear
Tear Gums
That is, the toothbrush delivers excessive brushing action to the teeth. The
excessive toothbrush action is harmful since it tears the gums and makes them
bleed. The teeth also may deliver a harmful action, by causing wearing of the
toothbrush.
Functional Modeling and Analysis Example
Figure 9.2 is a schematic view of an overhead projector. Figure 9.3 shows a
graph of the functional modeling and analysis diagram for the whole system.
In this functional analysis graph, E stands for electric field and M stands for
mechanical field. In this example, there are many chains of action; that is,
an object can be another object’s subject. Then we have a sequence of
subject-action-object-action chains. Each chain describes a complete
function. We can identify the following functions:
1. From electric power to image to screen, that is, the function of pro-
jecting an image in the film onto the screen. We can think of this as the
main basic function.