Simple Machines

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Simple Machines

• Making it Easy

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Simple machines

• Make force or effort easier
• Change direction of Force
• Increase speed
• Note machines dont make
• energy

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Levers

• A lever allows application of a force (effort) at
  a distance from the object to be moved (load).
• The further away the application of force the
  less input force is needed.
• Levers require a pivot or fulcrum where the lever
  can rotate around.
• Some levers have the effort closer than the load
  to speed up the movement

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Types of Levers

• CLASS 1
• Input Force lt Output Force
• Pivot in the middle
• CLASS 2
• Input Force lt Output force
• Pivot on the end
• CLASS 3
• Input Force gt Output force
• Pivot on the end

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Pulleys

• A single pulley changes the direction of Force
  only (Force In Force Out)
• Multiple Pulleys change direction and increase
  the Force (more pulleys more force e.g. a
  Block and tackle)

Fin
Fout 2 x Fin
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Wheel and Axle

• Wheels connected to axles turn a small force on
  the wheel into a large force on the axle e.g. car
  steering wheel, bikes, taps, spanners, crank
  handles
• The bigger the wheel, the easier the force
  required to turn the axle.

7
Inclined Plane

• A ramp makes lifting easier by increasing the
  distance you have to push it.
• A Wedge is a double inclined plane, good for
  pushing into a material
• E.g. axe head, knife, chisel
• A screw is a spiral ramp, when you twist, the
  material is pushed up the ramp.

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Gears

• Gears work on the same principle as wheels and
  axles transferring energy from a small wheel or
  gear to a large one to increase force or v.v.
  for increasing speed.
• Gears have teeth or cogs which enable
  intermeshing between wheels.
• Bevelled gears allow motion to be transferred at
  90.
• Worm gears have a spiral thread along a cylinder,
  acting as a single tooth making it very strong
  but slow.

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Force and Work

• Machines can increase or decrease force but they
  cant change mechanical energy.
• Mechanical energy is often called work because it
  makes things move.
• Work in machines is calculated using Force x
  distance.
• Work In Work Out if a machine is 100 efficient
  (no energy loss due to friction).
• In reality there is always some energy loss

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Calculating Input force required

• For a 100 efficient machine work is conserved
  i.e.
• Input force x distance to pivot Output force x
  distance to pivot
• In diagrams
• FI x di Fo x do
• These machines magnify input force

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Choose Force or Speed

• Machines increase force or increase speed, you
  cant have both! Why?
• How do you increase force?
• Decrease Distance to load
• Increase Distance to effort
• How do you increase speed?
• Increase Distance to load
• Decrease distance to effort