Levers

• Lever


  Contains 3 things: a fulcrum/pivot, a resistance, and an effort
• Example of a lever


  • Seesaw
• Fulcrum


  The point at which the lever pivots or moves
• Resistance


  The thing that needs to be moved
• Effort


  The force that is produced to move the resistance
• First order lever


  Fulcrum in the middle
• Second order lever


  Resistance in the middle
• Third order lever


  Effort in the middle
• Elbow extension is a first order lever
• Ankle plantar flexion is a second order lever
• Third order levers


  • Elbow flexion
  • All movements at the knees
  • All movements at the hips
  • All movements at the shoulders
• Load Arm (L)

  Distance between resistance and fulcrum
• Effort arm (F)


  Distance between effort and fulcrum
• In a second order lever, the effort arm is longer than the resistance arm, there is a mechanical advantage - can lift heavy loads with low effort
• In a third order lever, the resistance arm is longer than the effort arm, there is a mechanical disadvantage - cannot lift heavy loads
• First order levers do not have a clear mechanical advantage or disadvantage as the fulcrum is in the middle
• FL3

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