Six Simple Machines Chapter 4 section 3

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Six Simple MachinesChapter 4 section 3

• Inclined Plane
• Wedge
• Screw
• Wheel and Axle
• Lever
• Pulley

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Force

• Any push or pull is defined as a force
• The unit of force is the newton
• 1 pound 4.5 newtons

3
Work

• A force applied through a distance
• W F x d
• units of work are Newton meters (N ? m) but are
  commonly called Joules

4
Power

• Power is the measure of work done in a given
  time.
• The formula for power is
• P W/t
• The unit of work is the watt ( J/s)
• Since this unit is very small the Kilowatt is
  often used 1000 watts.

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Inclined Plane

• Also known as a ramp a flat sloped surface.
• How it works
• Allows you to exert your force over a longer
  distance.
• Input force force you use to push or pull the
  object
• Output force the force you would need to lift
  the object without the inclined plane
• Output force is equal to the objects weight

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Inclined plane - Mechanical Advantage

• IMA length of incline
• Height of incline
• Example if you are loading a truck that is 1
  meter high using a ramp that is 3 meters long,
  the
• IMA 3m / 1m 3
• Therefore the inclined plane increases the force
  you exert on the object by three times.
• By increasing the length of the incline, the less
  input force needed to push or pull the object.

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Wedge

• A device that is thick at one end and tapers to
  thin edge at the other end.

Input force
wedge
Output force
Output force
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Wedge How it works

• Instead of moving an object along an inclined
  plane, you move the inclined plane itself.

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Screws

• An inclined plane wrapped around a cylinder
• The threads act like an inclined plane to
  increase the distance over which you exert an
  input force.
• The threads exert an output force on the wood,
  pulling the screw into the wood.
• The friction between the wood and the screw holds
  the screw in place.
• The closer the threads are the greater the
  mechanical advantage.

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Levers

• A rigid bar that is free to pivot, or rotate, on
  a fixed point.
• The fixed point that a lever pivots around is
  called a fulcrum
• 3 classes, based on location of fulcrum,
• effort force (E) and resistance force (load) (R)

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First class lever

• Fulcrum is in between the effort force and the
  resistance
• Ex. Scissors, crowbar, car jack, prying the lid
  using a screw driver

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Second class lever

• Fulcrum is at one end, effort is at the other
  end, the resistance is in between
• Ex. Wheelbarrow, a Door, a Nutcracker,

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Third Class levers

• Fulcrum is at one end , effort force is close to
  fulcrum, resistance is at other end
• Almost all sports equipment ex.
• Golf club, baseball bat, lacrosse stick, fishing
  rod, rake, hockey stick etc.

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Mechanical advantage

• Ratio of the output force to the input force
• IMA ideal mechanical advantage, does not
  include friction
• IMA Formula
• Effort arm distance (cms)
• Resistance arm distance (cms)

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Actual Mechanical advantage

• Measures ratio of resistance force to effort
  force, includes friction
• Formula
• Resistance Force(g)
• Effort Force(g)

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Mechanical Advantage

• When MA is less than one the machine multiplies
  speed
• When the MA is greater than one the machine
  multiplies your effort

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Wheel and Axle

• a simple machine made of two circular or
  cylindrical objects fastened together that rotate
  about a common axis
• The object with the larger radius is the wheel
• Example screw driver
• It works because the wheel is larger than the
  axle, the axle rotates and exerts a large output
  force.
• The greater the ratio between the radius of the
  wheel and the axle the greater the mechanical
  advantage.

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Pulley

• A simple machine made of a small grooved wheel
  and a rope or cable wrapped around it
• Pulleys decrease the amount of input force
  needed to lift the object and it can change the
  direction of the input force.
• Example raising a flag pole.
• Two basic types
• A. fixed pulley-pulley that is attached to a
  structure
• B. movable pulley- pulley attached to a
  structure that can move

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The ideal mechanical advantage is equal to the
number of sections of rope that support the
object
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• Compound machine- utilizes two or more simple
  machines
• Apple peeler, bicycle