Why are there three classes? There are three classes of levers because all are classified by the locations of the fulcrum, the input force, and the output force.
Key Terms: Effort/Input (E)- The force a person uses when they use the lever Load/Output (L)-The force needed to move the object without a lever Fulcrum (F)- the pivot point (i.e. the elbow of an arm)
First-class lever: A first-class lever always has the fulcrum between the effort and load forces.
Why the mechanical advantage is always greater than, less than, or equal to 1: The mechanical advantage of a first-class lever would be greater than 1 because the fulcrum would be closer to the load arm which makes the effort arm longer. The mechanical advantage would be less than 1 because the fulcrum would be closer to the effort arm making the load arm longer. When the mechanical advantage is equal to 1 it's because the fulcrum would be in the middle making the effort arm and load arm equal to each other.
Example of a first-class lever: A crowbar and a wooden box. The fulcrum in the crowbar is where the crowbar is touching the wooden box. The effort force is the hand pushing down on the crowbar. The load force would be the tip of the crowbar, pushing the wooden box upward.
Photograph of a crowbar prying a nail, with the load, force and fulcrum labeled.
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Why are there three classes?
There are three classes of levers because all are classified by the locations of the fulcrum, the input force, and the output force.
Key Terms:
Effort/Input (E)- The force a person uses when they use the lever
Load/Output (L)- The force needed to move the object without a lever
Fulcrum (F)- the pivot point (i.e. the elbow of an arm)
First-class lever:
A first-class lever always has the fulcrum between the effort and load forces.
Why the mechanical advantage is always greater than, less than, or equal to 1:
The mechanical advantage of a first-class lever would be greater than 1 because the fulcrum would be closer to the load arm which makes the effort arm longer. The mechanical advantage would be less than 1 because the fulcrum would be closer to the effort arm making the load arm longer. When the mechanical advantage is equal to 1 it's because the fulcrum would be in the middle making the effort arm and load arm equal to each other.
Example of a first-class lever: A crowbar and a wooden box.
The fulcrum in the crowbar is where the crowbar is touching the wooden box. The effort force is the hand pushing down on the crowbar. The load force would be the tip of the crowbar, pushing the wooden box upward.