Statics: Bending of a beam/evenly distributed force problem

AI Thread Summary
The discussion centers on a statics problem involving bending stress in specific incisions. The user seeks clarification on the calculation of bending moment (Mb) at incision 2, particularly the term involving the evenly distributed force (q). There is confusion about the factor of 1.25 used in the equation, as the user expected it to be divided by 2 instead. Additionally, there are questions about the symbols used, specifically aA and Mb, and the reactions at points A and B. The conversation suggests starting with equations for bending moments to better understand the problem.
hattori_hanzo
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Hello, and sorry for my English, as I am Norwegian.

I have a statics problem which I can not understand.

I've taken a pic from my book:
eFcrt.jpg


The problem asks me to find the largest bending stress, σb, in the incisions 1 and 2.

I have the solution in front of me, I just don't understand what they have done with the evenly distributed force (q). Especially in incision 2, when they find Mb, they have used: Mb = FA*aA-q*2.5m*1.25.

The q*2.5m I can understand, but where does the 1.25 come from? I thought it should be divided by 2?

Can someone explain how this works for me?
 
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Especially in incision 2, when they find Mb, they have used: Mb = FA*aA-q*2.5m*1.25.

Please confirm what the symbols stand for.

In particular what is aA and Mb ?

You have not provided symbols for the reactions at A and B?
Do you know how to calculate these reactions?

You should start by writing the equation for the bending moments for 16.2 and 16.3, using x for the horizontal axis and starting with x=0 at A. Can you do this?
It will have the form M = some function of x and the loads to the left of x.
 
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