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AIM: What are Simple Machines

AIM: What are Simple Machines. Vocabulary. Definition of a Simple Machine. Makes work easier by changing either The amount of the force needed Or the direction of the force. Inclined Planes. An inclined plane is a flat surface that is higher on one end

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AIM: What are Simple Machines

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  1. AIM: What are Simple Machines

  2. Vocabulary

  3. Definition of a Simple Machine • Makes work easier by changing either • The amount of the force needed • Or the direction of the force

  4. Inclined Planes • An inclined plane is a flat surface that is higher on one end • Inclined planes make the work of moving things easier

  5. MECHANICAL ADVANTAGE • Is a measure of the “goodness” of a machine • The higher the MA the better? • What force acts/work against MA? • EFFICIENCY: less friction = greater Efficiency

  6. length height l h length of ramp height of ramp Inclined Plane • Sloped surface used to make lifting easier • MA =

  7. Screws • A screw is an inclined plane wrapped around a shaft or cylinder. • The inclined plane allows the screw to move itself when rotated.

  8. Don’t measure the top! gap  twice the radius of rod radius of rod 2  rr lg length of gap Note: 2  r =  d The Screw • A screw is an inclined plane wrapped around a rod • Use to hold objects together • MA =

  9. Wedges • Two inclined planes joined back to back. • Wedges are used to split things.

  10. width height h w height of wedge width of wedge Wedge • A wedge is an inclined plane with two sloping surfaces • Used to cut • MA =

  11. Wheels and Axles • The wheel and axle are a simple machine • The axle is a rod that goes through the wheel which allows the wheel to turn • Gears are a form of wheels and axles

  12. Pulleys • Pulley are wheels with a groove around the outside • A pulley needs a rope, chain or belt around the groove to make it do work

  13. Three Types of Levers • All levers have a fulcrum

  14. Levers-First Class • In a first class lever the fulcrum is in the middle and the load and effort is on either side • Think of a see-saw

  15. Levers-Second Class • In a second class lever the fulcrum is at the end, with the load in the middle • Think of a wheelbarrow

  16. Levers-Third Class • In a third class lever the fulcrum is again at the end, but the effort is in the middle • Think of a pair of tweezers

  17. Levers • A lever is a bar that is free to move about a pivot point • A lever has three parts • effort arm • fulcrum • resistance arm resistance arm effort arm fulcrum

  18. Second Class First Class Third Class Types of Levers • Levers are grouped into three classes

  19. First Class Lever • Fulcrum in the middle of the bar • Examples • Balance • Paint can • Teeter-totter resistance force effort force

  20. Second Class Lever • Resistance force (load) is in the middle • Examples • wheel barrow • door • nut cracker resistance force effort force

  21. Third Class Lever • Effort force is in the middle • Examples • baseball bat • fishing pole • canoe paddle • broom resistance force effort force

  22. length of effort arm le lr length of resistance arm resistance arm effort arm Mechanical Advantage of Levers • MA =

  23. Wheel and Axle smaller wheel • Two wheels of different sizes • Connected and move together • Examples • door knob • pencil sharpener • screw driver larger wheel

  24. Large force out small force in Wheel and Axle • A wheel and axle act like a circular lever. • By turning the large blue wheel, • The smaller yellow axle also turns.

  25. Large distance out Small distance in Wheel and Axle • Or, the two can be used in reverse. • By turning the small yellow axle • The larger blue wheel also moves.

  26. radius of wheel rw ra wheel  axle radius of axle MA of Wheel and Axle • MA =

  27. Pulleys • A pulley is a surface with a chain or rope going around • Used to lift heavy objects • Two types • Fixed • movable

  28. Types of Pulleys fixed pulley • Fixed Pulley • Pulley is fastened into position • Changes the direction of force • Does not magnify the force

  29. Types of Pulleys • Movable Pulley • Pulley is fastened to the load • Load is shared between both ends of the line • Only half the force is needed to lift the load movable pulley

  30. MA = 1 One line is supporting the load. MA = 2 Two lines are supporting the load. MA of a Pulley • MA = number of lines supporting the load • Don’t count the line that is being pulled.

  31. Efficiency •Efficiency is the ability to convert input work into actual work output. • no machine is perfect • loss caused by friction

  32. Output Work WO WI • Efficiency = 100 Input Work Calculating Efficiency • Ideal machines have 100% efficiency.

  33. Compound Machines • A compound machine is a combination of simple machines that work together.

  34. Simple Machines • Simple Machines can be put together in different ways to make complex machines • A complex machine is one or more simple machines

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