Notes
Slide Show
Outline
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Types of Simple Machines
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The Lever
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The Lever
a rigid bar that is free to turn about a fixed point called the fulcrum
  • Every Lever has three (3) parts:
  • 1.  Resistance Force, Input Force or Load, What you are trying to move or lift.
  • 2.  Effort Force or Output Force - The work done on the Lever.
  • 3.  Fulcrum – A fixed pivot point.
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The Lever
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1st Class Lever
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1st Class Lever
  • The Fulcrum (fixed pivot point) is located between the Effort (Input) and the Resistance (Output) Forces.
  • The effort and the resistance move in opposite directions.
  • The effort force pushes down in order to lift the resistance or load.
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1st Class Lever
  • When the fulcrum is closer to the effort than to the load:
    •  there is a loss in force
    • There is a gain in speed and distance.
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1st Class Lever
  • When the fulcrum is closer to the load than to the effort:
    •  there is a loss in speed and distance
    • There is a gain in force.
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1st Class Lever
  • When the fulcrum is midway between the effort and the load:
    •  there is no change in force, speed or distance
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1st Class Lever
  • Examples:
    • Seesaw
    • Crowbar
    • Scissors
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2nd Class Levers
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2nd Class Lever
  • The load is between the effort and the fulcrum.
  • The fulcrum is at one end of the lever.
  • The fulcrum is usually closer to the load.
  • Produce a gain in force.
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2nd Class Levers
  • Examples:
    • Wheelbarrow
    • Bottle opener
    • Nutcrackers
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3rd Class Levers
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3rd Class Levers
  • The effort is between the load and the fulcrum.
  • There is usually a loss in force, but a gain in speed and distance.


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3rd Class Levers
  • Examples:
    • Broom
    • Shovel
    • Fishing rod
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The Pulley
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The Pulley
  • A pulley changes the direction of the force:
    • Instead of lifting up, you can pull down using your body weigh against the load (what is being lifted)
  • A pulley gains nothing in force, distance or speed


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The Pulley
a wheel that turns around an axle
  • A pulley is a grooved wheel that turns around an axle (fulcrum), and a rope or a chain is used in the grove to lift heavy objects.
  • A pulley may be fixed, moveable, or used in combination.
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The Fixed Pulley
  • Is attached to something that doesn't move such as the ceiling or wall)
  • It acts as a first class lever with the fulcrum located at the axis
  • Instead of a bar the pulley uses a rope or chain.
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The Pulley
  • A moveable pulley acts as second class lever
    • the load is between the fulcrum and the effort
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The Pulley
  • A compound pulley is a system of movable pulleys.
  • Mechanical advantage can be increased by using more than one pulley.
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The Inclined Plane
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The Inclined Plane
a sloping surface that does not move
  • An inclined plane provides for NOT Less work but less effort.
  • The trade off is greater distance to travel.
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The Inclined Plane
  • Used to reduce the force needed to overcome the force of gravity when lifting or lowering a heavy object.
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The Inclined Plane
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The Screw
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The Screw
an inclined plane wrapped around a central cylinder
  • A Screw has two (2) parts:
    • The Body – Cylinder Post
    • The Thread – Inclined Plane wrapped around the cylinder.
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The Screw
  • Functions of the screw
    • To fasten things – the standard screw or nuts & bolts.
    • Drill bits are screws used to make holes.
    • A jackscrew is used to lift heavy objects; car jack.
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The Screw
  • When you turn a screw:
    • The input force is changed by the threads into an output force.
    • The output force pulls the screw into the materials.
    • Friction between the threads & the material holds the screw in place.


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The Wedge
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The Wedge
an inclined plane that tapers to a sharp edge
  • The wedge used to increase force.
  • The material remains in place while he wedge moves through it.
  • A wedge changes the direction of the input force.



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The Wedge
  • Wedges can be forced between two things to hold them tightly together, like nails or a doorstop.
  • Wedges can be used to split, cut or fasten.
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The Wheel & Axle
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The Wheel & Axle
a wheel connected to a rigid pole
  • The Wheel & axle is a modified lever:
    • The center of the axle acts as a fulcrum – making the wheel a lever that rotates around in a circle.