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Thursday, December 29, 2011

Third-Class Levers

The third type or lever is the third-class lever, in which the fulcrum is at one end, with the load at the other end and the effort in the middle. The direction of the load force is opposite to the resistance. Here are a couple of examples of third-class levers: tweezers and the human jaw. In a pair of tweezers, the fulcrum is the end with the two pieces connected. To use them, you squeeze or release the middle. When you squeeze the tweezers, they close down, and when you release them, the open up. In a similar way, when you bite down, the effort is felt in the middle of your line of teeth. But most of the biting control is in your front teeth.

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