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The different types of levers in the human body. These levers consisting of First Class Lever, Second Class Lever, and a Third Class Lever. The list below describes such skeletal movements as normally are possible in particular joints of the human body.
English: Within the human body there are 3 types of levers. The first class lever which can be seen, is located in the head. The second class lever is located within the leg. Finally, the third class lever is located in the arm.
A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum.A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load, and effort, the lever is divided into three types.
English: Labeled diagrams of various parts of the human body in relation the the lever classifications exemplified by the joint (neck, foot, and arm). Credit to Anatomography, Cervical Vertebrae. CC BY-AS 2.1 JP.
In the example of a nail clipper on the right (a compound lever made of a class 2 and a class 3 lever), because the effort is applied vertically (that is, not perpendicular to the lever), distances to the respective fulcrums are measured horizontally, instead of along the lever. In this example, W/F is 7 + 1 / 1 × 6 / 6 + 2 = 6.
Where a lever rotates continuously, it functions as a rotary second-class lever. The motion of the lever's end-point describes a fixed orbit, where mechanical energy can be exchanged. (see a hand-crank as an example.) In modern times, this kind of rotary leverage is widely used; see a (rotary) 2nd-class lever; see gears, pulleys or friction ...
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The wheelbarrow is designed to distribute the weight of its load between the wheel and the operator, so enabling the convenient carriage of heavier and bulkier loads than would be possible were the weight carried entirely by the operator. As such it is a second-class lever. Traditional Chinese wheelbarrows, however, had a central wheel ...