Machines and Mechanical Advantage

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Machines and Mechanical Advantage
   Archimedes (Greek mathematician, 287 to 212
B.C.) said, Give me a place to stand and I will
move the Earth, meaning that if he had a lever
long enough, he could move the Earth by his own
effort
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Mechanical Advantage (M.A.)

• the number of times a machine multiplies the
  input force (FI )
• the more times the machine multiplies the input
  force, the easier the job (requires less force
  by us)

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Mechanical Advantage formula
MA FO FI
MA Mechanical Advantage FO Output Force or
Load FI Input Force
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Example problem using forces

• What is the mechanical advantage of a machine
  where an input force of 20 N will put out a force
  of 180 N?

given formula
set up problem answer w/ unit
of measurement
FO 180N MA FO 180N/20N
9 FI 20N FI
There is no unit of measurement on mechanical
advantage, it is simply a ratio
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Six Types of Simple Machines
The Inclined Plane Family
1. Inclined Plane

• basically a ramp
• has no moving parts
• decreases the input force needed to move an
  object but increases the distance necessary to
  move it

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2. Wedge

• an incline plane that moves through something
• normally made up of two inclined planes

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3. Screw

• an inclined plane that is wrapped around to form
  a spiral
• multiplies the input force by increasing the
  distance

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4. Lever
The Lever Family

• a rigid bar that is free to pivot on a fulcrum
• Three classes of levers
• First Class

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• Second class

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• Third class
• the only lever that does NOT multiply the input
  force
• but does increase speed and distance of what you
  are moving

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5. Pulley

• a rope, belt, chain wrapped around a grooved
  wheel
• may change the direction of the force
• may multiply the effort force to lift heavy loads
  when using many pulleys

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6. Wheel and Axle or Gears

• a lever or pulley connected to a shaft
• the wheel/gear is the larger circle/lever/pulley
• the axle is the smaller circle/shaft/axle

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Compound Machines

• a combination of two or more simple machines

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