Simple Machines

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Simple Machines
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Machines

• Lever
• Inclined plane
• Pulley
• Screw
• Wedge
• Wheel axle

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Machines

• Device to multiply force or change its direction
• Cant increase work done
• Work put into machine must be at least as great
  as the work output of machine

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Machines

• Since work is force times distance, input force
  can be decreased by increasing input distance
  force is multiplied
• Work is made easier because less force is needed
• Sometimes output distance is increased by
  increasing input force distance is multiplied

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Efficiency

• Work output divided by work input (x 100 for )
• A measure of losses due to friction
• Efficiency is always less then 100

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Mechanical Advantage

• A measure of how much the effect of the force is
  increased
• Actual M.A. is ratio of output force to input
  force
• Theoretical M.A. can be found from the design of
  the machine

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Mechanical Advantage

• For lever, theoretical MA is input distance /
  output distance
• For inclined plane it is plane length / height
• For pulley system it equals the number of cords
  supporting the weight being lifted

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Summary

• Machines help us do work by using less force over
  greater distance
• Mechanical Advantage output force / input force
• Efficiency work out / work in