Third-class lever

In a third-class lever, the effort force lies between the resistance force and the fulerum. Some kinds of garden tools are examples of third-class levers. When you use a shovel, for example, you hold one end steady to act as the fulcrum, and you use your other hand to pull up on a load of dirt. The second hand is the effort force, and the dirt being picked up is the resistance force. The effort applied by your second hand lies between the resistance force (the dirt) and the fulcrum (your first hand). 

Figure 13 (a) Example of the first-class lever system, (b) Example of the second-class lever system, (c) Example of the third-class lever system and single-segment static analysis. (Adapted from Troup and Edwards, reproduced with permission of the Controller of Her Majesty s Stationery Office)... 

A second-class lever would he the wheelbarrow where the wheel serves as the fulcrum (Figure 10-7). The length of the lever arms and the position of the load determine the mechanical advantage gained. A third-class lever is... 

FIGURE 10-8 The third-class lever has the fulcrum at one end of the arm and its force is applied along the lever s arm. A baseball bat operates as a third-class lever. 

A third-class lever has the point of effort between the fulcrum and resistance. 

Of the three levers, the second-class lever is most efficient with regard to minimizing effort needed to move a resistance. A wheelbarrow is an example of such a lever. Most of our long muscles act as third-class levers. The biceps muscle s flexion effort in moving the forearm is... 

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