Hobbies And Interests
Three Classes of Levers
The first class of levers is what we would think of as a teeter-totter: The fulcrum sits in the middle, and the load and applied force are at opposite ends. The second class is what we would think of as a wheelbarrow: The fulcrum is at one end, the applied force is at the other and the load is in the middle. The third class of lever works like a fishing pole: The fulcrum is at one end, the load at the other and the applied force in the middle.
Knowing Your Load
The first safety rule for levers is to know your load. This concept applies across all three classes of levers. To protect the lever's infrastructure (and yourself), make realistic demands on the lever's capability. Otherwise, your lever will reach a breaking point and snap, putting you and those around you in danger.
Fulcrum Placement
Understanding fulcrum placement will help you avoid circumstances that put the infrastructure of your lever in jeopardy. Remember, placing the load closer to the fulcrum always decreases the applied force needed for using the lever, thus making it safer. Less applied force means less effort, translating to a decreased risk of straining your muscles or back.
About Third-Class Levers
Since third-class levers place the fulcrum at the end and the applied force in the middle, they do not provide any mechanical advantage. In fact, third-class levers require an applied force larger than the load. For this reason, a 10-lb. fish at the end of a fishing pole feels like it weighs more than 10 lbs. Keep this caveat in mind when using third-class levers to bear loads and determining which objects are safe to lift.