Simple and Compound Machines
A quick review:
Simple machines are non-motorized devices that change the direction or magnitude of a force. 6 basic
types are: lever, pulley, wheel and axle, inclined plane, screw, and wedge.
Compound machines (high school only): More than one simple machine connected to each other.
Efficiency: The comparison of IMA to AMA. How good is the simple machine at doing its job?
IMA= Ideal Mechanical Advantage. In a perfect system with no friction or loss of energy, your ratio of
output to input force.
AMA= Actual Mechanical Advantage. Actual output force/actual input force. Takes into account factors
influencing actual work done, such as friction, flex, wear.
Coefficient of Friction (high school only): the ratio of the force of friction between two bodies and the
force pressing them together. Essentially, how well things stick to each other due to friction.
Lever: Has a fulcrum, load and effort that act on an arm.
Further divided into 3 classes:
Class 1= seesaw. Fulcrum in center
Class 2= wheelbarrow. Load in center
Class 3= arm. Effort in center
Inclined Plane: an angled surface used to raise or lower
a load, uses less force than vertically lifting, but over a
greater distance. IMA= ratio of the length of the sloped
surface to the height it spans.
Wedge: Triangular shaped, forces 2 objects apart. Must make output force perpendicular to input force.
IMA= length of slope divided by width of wedge
Pulley: a wheel on an axle that moves freely (not
rigidly attached) to reduce friction. IMA= count strings
Wheel and Axle (WAX): a wheel and axle attached to each
other so that turning one turns the other. IMA= radius of
wheel divided by radius of axle
Screw (High school only): converts rotational motion to
linear motion. IMA=ratio of the circumference of the
screw to the distance it advances during each
revolution
Other things to know:
History: Honestly, Wikipedia goes into plenty of depth on this for each machine type.
The event will be on static mechanics, not dynamic (machines/systems will be constant).
There are hundreds of websites, tutorials, and videos to teach simple machines.
Diagrams borrowed from
http://www.phy.ilstu.edu/pte/489.01content/simple_machines/simple_machines.html