Question

When is a lever called a lever of Class Ill? Give two examples.

Answer 1

1. Class 3 levers are those levers in which the fulcrum and load always take the endpoint positions of the lever.
2. The effort may lie at any position between the endpoints fulcrum and load.
3. The load and the effort always need to be in opposite directions.
4. The effort arm is always shorter than the load arm.
5. Mechanical advantage is defined as the ratio of load to effort, or it can also be defined as the ratio of effort arm to load arm.$\mathrm{Mechanical}\mathrm{advantage}=\frac{\mathrm{load}}{\mathrm{effort}}=\frac{\mathrm{effort}\mathrm{arm}}{\mathrm{load}\mathrm{arm}}$ , when effort arm < load arm, M.A < 1
6. Since mechanical advantage is less than 1, class 3 levers result in a gain in speed.
7. Both mechanical advantage and velocity ratio will have a value less than 1.
8. In the case of fire tongs, the red-hot coal piece is clamped at one end, while the fulcrum lies at the curve portion of the tong, and effort is applied at some distance from the fulcrum.
9. In the case of the broom, the effort in the form of input force is shown to lie between the load i.e., output force and fulcrum.