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Simple Machines

Simple Machines. Work, Mechanical Advantage and Efficiency. Essential Question : What is the relationship between IMA & MA . Simple Machines. All machines can be classified as or a combination of levers and inclined planes . Manipulate the Law of Conservation of Energy

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Simple Machines

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  1. Simple Machines Work, Mechanical Advantage and Efficiency Essential Question: What is the relationship between IMA & MA

  2. Simple Machines • All machines can be classified as or a combination of levers and inclined planes. • Manipulate the Law of Conservation of Energy • The amount of energy that goes in the machine = to the amount of energy that comes out. • Work in = Work out • Fin x d in = F out x d out

  3. Machines and Work • Machines DO NOT decrease work!!! • They change the Force and distance needed to get a certain amount of work done. F d F d F d

  4. F in x d in = F out x d out Work Done Fin x 1.75 m = 2000 N x 0.25 m Fin 2000 N x 0.25 m = Fout 1.75 m 286 N Fin = d in= 1.75 m 2000 N Fulcrum/ Pivot point d out= 0.25 m

  5. Mechanical Advantage • How much a machine changes the force • There are 4 variables • Fe = “effort force”: how much YOU put in. • Fr = “resistance force”: force generated by machine. • de = “distance effort”: distance effort must travel i.e. length of a lever’s effort arm. • dr = “distance resistance”: distance the resistance must travel i.e. the length of the resistance arm in a lever.

  6. Mechanical Advantage Fr Fe d e Fulcrum/ Pivot point d r

  7. Ideal Mechanical Advantage • Model of a machine in an “ideal” world. • No friction or heat loss. • Ideal mechanical advantage = distance effort/distance resistance • IMA = de/dr • This is a ratio so there are no units

  8. Mechanical Advantage • In the “real” world energy is lost as friction and heat. • Mechanical Advantage = resistance force/effort force • MA = Fr/Fe • No units

  9. Efficiency • Workout / Workinx 100 • The ratio of a machine’s MA to its IMA determines its efficiency. • Efficiency = MA / IMA x 100.

  10. Levers • Label • Fe = “effort force” • Fr = “resistance force” • de = “distance effort” • dr = “distance resistance” • 3 lever types • Class 1 lever: • Ex: crowbar Fe Fr d e d r Fulcrum/ Pivot point

  11. Levers • Label • Fe = “effort force” • Fr = “resistance force” • de = “distance effort” • dr = “distance resistance” • Class 2 lever: • Ex: wheel barrow Fr d r Fulcrum/ Pivot point Fe d e

  12. Levers • Label • Fe = “effort force” • Fr = “resistance force” • de = “distance effort” • dr = “distance resistance” Class 3 lever: • Ex: bicep Fr d e Fulcrum/ Pivot point Fe d r

  13. Inclined Plane • Example: ramp de dr Fe Fr

  14. More simple machines • Wedge: • Screw: • Wheel and axle: • Pulley: Inclined plane Inclined plane wrapped around a cylinder Lever Variation of wheel and axle

  15. Height does not change, only the angle. Height = 0.5 m

  16. Scale reads = 300g Car mass = 500g Height = 0.5 m Length = 0.83 m 300

  17. Modified test Scale reads = 3N Car mass = 5N Height = 0.5 m Length = 0.83 m 300

  18. Scale reads = 300g Car mass = 400g Height = 0.5 m Length = 0.66 m 300

  19. Distance Force Force Distance Inclined Plane • Example: ramp de dr Fe Fr

  20. Mechanical Advantage Example Fe 200 N Fr 75N 1 m 4 m d e d r

  21. 500 N

  22. Class 1 lever Class 2 lever Class 3 lever Fr Fe Fe Fr Fr Fe dr de de dr dr de Fe Fr de dr

  23. Force Resistance Fulcrum

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