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Choice of diagram
I have changed the diagram in the lede of this article. See my diff.
The original diagram showed negative shear force where the slope of the bending moment line was positive; and positive shear force where the slope of the bending moment line was negative. This is contrary to the diagram and sign convention at Shear and moment diagram. It is also contrary to the equation that states the shear force is equal to the derivative of bending moment with respect to distance along the beam:
- where V is shear force and M is bending moment at a distance x from a support
The original diagram was created by User:Cdang on Wikimedia Commons. I have discussed the situation with him and he stated that the diagram was prepared for, and is used on, French Wikipedia. His orientation of shear force and bending moment are common in Europe and match his source document which is in the French language. Cdang has told me that he is happy with the diagram he created, and has no objection if English Wikipedia uses a different diagram. (See my Talk page on Wikimedia Commons.)
The discussion of positive and negative bending moment in the beginning should be revised. It is unclear and the sign convention of negative moment creating sagging seems not to be the standard. Sadly I am too busy too look into it closer. — Preceding unsigned comment added by 220.127.116.11 (talk) 07:51, 23 October 2015 (UTC)