eli5: moments about a specified axis? conceptual understanding.

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Yes, I know the formula is U dotted with (r x F), but I have no conceptual understanding. Any video or text I find, just tells me how to do it…but I have no idea what I am doing. How does the dot product help with this, I just expect something… cross-product related only.

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How does dotting the unit vector of a specified axis with the moment vector we calculated give us the moment around said specified axis. Do I just have a dumb understanding of the dot-product? Can someone kindly explain like I am 1.

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Anonymous 0 Comments

M is the magnitude of the moment, a dimensionless scalar. U is the unit vector, which defines the direction around which the moment acts. It’s a dot product because you might calculate a moment force that rotates around an axis that doesn’t align with the any of the x,y, or z axes. By using the dot product, you can calculate the total magnitude of M when it doesn’t align with an axis.

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