
After a product has been selected, a nondestructive Functional Analysis is performed.
 The product’s purpose is identified.
 Observations are made to determine how the
product functions. These observations are
recorded in detail.
 The system’s inputs and outputs are identified.
 A theory of operations is developed and recorded.



A theory of operation is a description of how
the product works and how it is used.
Prepare a concise “theory of operations”
(black box) that describes how you think your
product functions . You will contrast this to
what you discover after you disassemble your
product.
NOTE: you can prepare this a table in MS
Word as part of your board presentation.
An example: Theory of Operation for a fish finder.
What is the
product?
How does it
work (your
theory)?
What does it
do
(purpose)?
How is it
used?
What are the major
parts? Simple
Machines?
Source: Airmar technology. (2012, March 28). Retrieved from
http://www.airmartechnology.com/uploads/installguide/Theory_of_ Operations.pdf
Inputs
Black Box
Output
Product Function

It is a non-destructive method of analysis
used to identify the sequential operations
of a product or system and identify the
inputs and outputs of those systems.

A black box systems model is used to identify what goes into and out of
the product in order to make it work as a system.

The black box is a model used to represent the product’s internal
components or processes, which may be unknown at this point.

Describe the expected
purpose of the
product.
The purpose of a
toothbrush is to clean
teeth and gums to
prevent tooth and gum
decay.
 Water and a cleaning
paste are also used in
with the brush.

Inputs
Black Box
Output
Product Function
• Hand
motion
• Energy
• Toothpaste
• Water
•
•
•
•
Batteries
Motor
Switch
Circuit board
•
•
•
•
Sound
Heat
Waste
Clean teeth
and gums
The engineer makes an
annotated sketch of
the product and labels
all of the visible
components.
 This information is
used to write up a
detailed analysis of the
object’s sequential
operation, or function.

1.
2.
3.
4.
5.
6.
Describe the product and its purpose or primary function. Include
manufacturer or brand name, if visible.
Sketch an isometric pictorial of the product in your engineer’s notebook
(both students do their own), and label the individual components. Describe
and label the visible components. If you are not sure what a particular
component is called, make up a descriptive label. Scan this for use later.
Create a “black box systems model” and identify the system inputs and
outputs. Label the black box.
Black box: Make an educated guess about the product’s function that you
cannot identify, because the mechanical components are hidden from plain
view. Your “theory of operation” must include both the known (what you can
see) and the unknown (what you can guess).
Describe which simple machines are used and how they help make the
product perform its primary function.
This documentation should be in MS-Word and will become part of your
technical report. Until then, you must present it as a PPT slide with
illustrations.

Machines consist of
elements, such as wheels and
axles, that work together
(inputs) to transmit force and
produce work (output).

No matter how complex, all
machines are based on one
or more simple machines
that change the direction or
magnitude of an applied
force.

This change in force is
referred to as “mechanical
advantage.”
Explore types of levers by clicking 
Class 1
Class 2
Class 3

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



Wheel and axle
Pulley
Lever
Inclined plane
Wedge
Screw
You will be expected to identify the simple machines in your product in your analysis.


Work indicates that a force is exerted and is
moving something
Simple machines make work easier
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
© iStockphoto


Work is the transfer of energy from one
system to another
Mechanical work is the product of the
magnitude of force in the direction of
displacement and the distance through which
a body moves
Displacement

Two connected
circular objects of
different
diameters
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart

Gear
 Wheel with teeth
 Teeth of one gear push
against teeth of another
gear
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart

A wheel (and axle)
with a rope running
over it
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart


A pulley can change
the direction of force
Multiple pulleys in
combination can
reduce the effort
force to move an
object
10 lb
10 lb
80 lb
10 lb
10 lb

A bar that is free to pivot
around a fixed point
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart

Three components
 Resistance Force
 Effort Force
 Fulcrum
Resistance
Effort
Fulcrum

Three types
Levers Have a Lot of Class. (n.d.). Retrieved from City Tech: http://citytechnology.org/stuff-thatworks/levers-have-a-lot-of-class
 First Class
▪ Fulcrum between effort and resistance forces
▪ Effort and resistance forces in same direction
Effort
Resistance

Three types
Levers Have a Lot of Class. (n.d.). Retrieved from City Tech: http://citytechnology.org/stuff-thatworks/levers-have-a-lot-of-class
 Second Class
▪ Resistance force between fulcrum and effort force
▪ Effort and resistance forces in opposing directions
Resistance
Effort

Three types
Levers Have a Lot of Class. (n.d.). Retrieved from City Tech: http://citytechnology.org/stuff-thatworks/levers-have-a-lot-of-class
 Third Class
▪ Effort force between fulcrum and resistance force
▪ Effort and resistance forces in opposing directions
Resistance
Effort

Slanted surface
used to raise an
object
Microsoft Office Clipart
© iStockphoto
© iStockphoto
Microsoft Office Clipart

Wedge

Screw
Images from Microsoft Office Clipart



Inclined plane that moves
A triangle shape with a sharp
point
Can split, cut, tighten, or hold
things together
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart
Microsoft Office Clipart


Inclined plane wrapped around a shaft
Used to fasten things together or move
things
© iStockphoto
Worm gear
© iStockphoto
© iStockphoto
Corkscrew conveyor
© iStockphoto
Parking garage ramp
Microsoft, Inc. (2008). Clip art. Retrieved from http://office.
microsoft.com/en-us/clipart/default.aspx
Wikipedia. Retrieved from http://en.wikipedia.org
iStockphoto. Retrieved from http://www.istockphoto.com/index.php