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| Levers of the 3rd Order [Class III Levers] |
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| In class III levers effort is situated between the load and the fulcrum. (shown in the figure below) |
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| Lever of third order |
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| As effort is situated between the load and the fulcrum, load arm is always greater than the effort arm. M.A. of class III lever is always < 1. |
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| Gain in speed is obtained i.e., a larger movement of load is obtained by a smaller movement of effort. |
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| Some of the levers are classified on the basis of the position of the forces, as shown in the figure below. |
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| Levers classified by positions of the forces |
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| The diagram shows a lever in use. |
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| (i) To which class of lever does it belong? Give one example of this class. |
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| (ii) Calculate its MA if AB = 2.0 m, AF = 20 cm. |
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| (iii) Calculate the effort needed to lift the load. |
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| (i) Class I, example: scissors |
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| (ii) Load arm = AF = 20 cm. |
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| Effort arm = BF = AB - AF |
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| = 200 - 20 |
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| = 180 cm |
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