Simple Machines: Levers

First Class Levers
First class levers have the fulcrum placed between the load and the effort, as in the seesaw, crowbar, etc. If the two arms of the levers are of equal length, as with the balance scale, the effort must be equal to the load. If the effort arm is longer than the load arm, as in the crowbar, the effort travels farther than the load and is less than the load.  

 

Second Class Levers

Second class levers have the load between the effort and the fulcrum. The effort always travels a greater distance and is less than the load. Second class levers always multiply the input force, however they do not change its direction. They always have the output force between the fulcrum and the input force ensures that it has mechanical advantage. Wheelbarrows, staplers, pliers, nail clippers are all good examples of second class levers.

 

Third Class Levers

Third class levers have the effort placed between the load and the fulcrum. The effort always travels a shorter distance and must be greater than the load. An example of third class lever is the human forearm; the fulcrum is the elbow, the effort is applied by the biceps muscle, and the load is in the hand. Other examples of third class levers would include a baseball bat, a hammer driving in a nail to a piece of wood, tweezers, etc.