Question

Class III levers have the mechanial advantage less than 1. Why are they then used ?

Answer 1

A class 3 lever has the effort between the load and the fulcrum. Both the effort and load are in the same direction. Because of the configuration, the fulcrum must prevent the lever beam from moving upward or downward. Often a bearing is used to allow the beam to pivot
This means they do not provide a mechanical advantage. In fact, more force is required in a third class lever to move an object. Third class levers are used in applications where speed is important. Because a larger force is applied by the effort, the load travels a further distance.