Hibbeler Mechanics of Materials

[jaredogden]

Hey guys I'm looking through my Mechanics of Materials book (Hibbeler 8th ed.) and am quite confused at the section on shear and moment diagrams. I thought I grasped it very well in statics but I guess I was wrong. Anyways I am looking at Example 6.4 and it asks for the shear and moment diagrams of a beam.

The beam is 10m long and on the far left point A is supported by a roller and has a counterclockwise moment of 80 kN*m. moving to the right point B is located in the middle at 5m and there is a force in the negative y direction (assuming down is negative) and here starts a rectangular distributed force of 5 kN/m until point C at the end of the beam (10m from A) point C is a pin support.

The part of this problem that is tripping me up is the first thing they show is the sum of forces in the y direction and the equation is 5.75 kN-V=0. I have no clue where the 5.75 came from, or how they got it... I'm assuming I'm just overlooking something, or need to review some statics. Can anyone explain to me what Hibbeler did to get 5.75 kN?

Thanks for your time and help ahead of time

 

[AlephZero]

Start by finding the reactions at the supports.

You didn't give the magnitude of the force at B so we can't do the arithmetic, but I expect you will see where the 5.75 came from when you have the reactions.

 

[jaredogden]

I think I tired doing the sum of forces and couldn't get that answer. I talked to someone else in my class and they had the same problem with it too. The force at B is 15 kN

 

[jaredogden]

Scratch that I am an idiot.. I wish I could just delete this thread or something haha thanks for the help.

 

[pongo38]

You arguably learn more from being an idiot than from being a genius.

 

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2nd year eng nuig?? ha