Science 1: Simple Machines: Lever

Ideal Mechanical Advantage (IMA)

• The Ideal Mechanical Advantage for a lever is: IMA = r_E/r_L, where r_E is the distance from the fulcrum to the effort force, and r_L

• This applies to all 3 classes of levers.

Real-World Levers

• Levers can have less than 100% efficiency (or less than the IMA) for several reasons:

  1. friction
  2. the mass of the lever arm
  3. the forces do not remain parallel to the direction moved.
  4. the lever arm is elastic and can bend
  5. the lever arm and fulcrum can get "dented"
  6. buoyancy...
  temperature change

Example of Mechanical Advantage taking into account the arm mass:

In this picture, L is the length of the beam, L_L is the length of the beam that is on the load side of the fulcrum, and L_e is the length of the beam on the effort side of the fulcrum. If M is the mass of the beam itself, then the IMA is given by: