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The moment arm of a force about a specific axis of rotation can be found geometrically by constructing the force's line of action and then finding the shortest distance between the line of action and the axis. The procedure is shown in the figures below.
For vertical forces:
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Given forces. | Construct line of action for each. | Find the shortest distance (shortest distance |
For horizontal forces:
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Given forces. | Construct line of action for each. | Find the shortest distance (shortest distance |
General angles:
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Given forces. | Construct line of action for each. | Find the shortest distance. |
Key Points
Some key points to remember:
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