 |
| Levers of the 3rd Order [Class III Levers] |
 |
| In class III levers effort is situated between the load and the fulcrum. (shown in the figure below) |
| |
 |
| |
| Lever of third order |
| |
| As effort is situated between the load and the fulcrum, load arm is always greater than the effort arm. M.A. of class III lever is always < 1. |
| |
| Gain in speed is obtained i.e., a larger movement of load is obtained by a smaller movement of effort. |
| |
| Some of the levers are classified on the basis of the position of the forces, as shown in the figure below. |
| |
 |
| |
| Levers classified by positions of the forces |
| |
 |
| |
 |
| |
| The diagram shows a lever in use. |
| |
| (i) To which class of lever does it belong? Give one example of this class. |
| |
| (ii) Calculate its MA if AB = 2.0 m, AF = 20 cm. |
| |
| (iii) Calculate the effort needed to lift the load. |
| |
 |
| |
| (i) Class I, example: scissors |
| |
| (ii) Load arm = AF = 20 cm. |
| |
| Effort arm = BF = AB - AF |
| |
| = 200 - 20 |
| |
| = 180 cm |
| |
 |
| |