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Simple Machines

Simple Machines. A device created to make work easier. How do machines make work easier?. Machines can multiply the input force. Mechanical Advantage (Force out / Force in) Machines change the direction of the input force.

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Simple Machines

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  1. Simple Machines A device created to make work easier.

  2. How do machines make work easier? • Machines can multiply the input force. • Mechanical Advantage (Force out / Force in) • Machines change the direction of the input force. • Machines can never multiply work done that would violate the law of conservation of energy!

  3. What are three types of simple machines? • Lever • 1st Class • 2nd Class • 3rd Class • Wheel and Axel • Pulley • Inclined Plane • Fixed and moving

  4. Lever Classes

  5. First class lever: See Saw • E-F-R • Changes the direction of the input force. • Mechanical Advantage is adjustable. • Fin x d (effort arm) = Fout x d (resistance arm)

  6. Second Class: Wheel barrow • E-R-F • Always has a mechanical advantage greater than 1. • The Resistance will always move a smaller distance than the effort. • Effort and resistance move in the same direction.

  7. Third Class: Baseball Bat • F-E-R • Effort and motion are in the same direction. • Mechanical advantage is always less than 1 • Generally increase the speed of the lever.

  8. Pulley: Bicycle pedals • Fixed pulleys change direction but have no mechanical advantage. • Mobile pulleys increase mechanical advantage. • Each rope attached to the load supports an equal percentage of the load. • Multiple pulleys can greatly increase mechanical advantage. • As mechanical advantage increases so does distance.

  9. Count the ropes!

  10. Inclined planes: Ramps • The lower the angle generally the greater the mechanical advantage. • Reducing friction is the key. • Mobile inclined plane. An axe or a knife.

  11. Efficiency: Work out/ Wok in • How much energy can you convert to useful work? • Where does the energy go that is not converted into useful work? • The 2nd Law of Thermodynamics.

  12. What are the major sources of Energy lost for each of our machines? • Lever: • Pulley: • Inclined plane:

  13. What happens to these loses of energy as the mechanical advantage increases? • Lever • Pulleys • Inclined planes

  14. Is there ever a free lunch? • What is the general relationship between mechanical advantage and efficiency? • What implications does this have for our high energy use society? • How does this relate to respiration, combustion and photosynthesis? • Matter works in cycles? Does energy?

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