Lever first-class

A lever is a simple machine that consists of a rigid bar supported at one point, known as the fulcrum. A force called the effort force is applied at one point on the lever in order to move an object, known as the resistance force, located at some other point on the lever. A common example of the lever is the crow bar used to move a heavy object such as a rock. To use the crow bar, one end is placed under the bar, which is supported at some point (the fulcrum) close to the rock. A person then applies a force at the opposite end of the crow bar to lift the rock. A lever of the type described here is a first-class lever because the fulcrum is placed between the applied force (the effort force) and the object to be moved (the resistance force). 

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)... 

Three types of levers are based on the location of the fulcrum. The seesaw in Figure 10-6 is an example of a first-class lever. 

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

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). 

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