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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.
For example, a bench vise consists of a lever (the vise's handle) in series with a screw, and a simple gear train consists of a number of gears (wheels and axles) connected in series. The mechanical advantage of a compound machine is the ratio of the output force exerted by the last machine in the series divided by the input force applied to ...
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.
Oars are levers. Which class of lever depends on the frame of reference. From the rower's perspective, the oar can be seen as a Class I lever. The oar is fixed in the oarlock, the rower pulls on the handle, and the blade moves in the opposite direction to propel the boat. The blade is further from the oarlock than the rower's hands.
Pincers are first-class levers, but differ from pliers in that the concentration of force is either to a point, or to an edge perpendicular to the length of the tool. This allows pincers to be brought close to a surface, which is often required when working with nails .