Finding Moments of a Beam: Where Did I Go Wrong?

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SUMMARY

The discussion revolves around solving a static equilibrium problem involving forces and moments. The participant initially calculated the vertical force at point A (Fay) incorrectly, leading to confusion about its direction. After reevaluating the moments about point B, they determined that Fay equals 15 kN, while the force at point B (Fby) was established as 45 Newtons. The key takeaway is the importance of correctly interpreting the signs of forces and moments in equilibrium equations.

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Homework Statement


Find the Fay this is static equilibrium so ƩF=0 and ƩM=0

Homework Equations



ƩMa=0
= 2x5 + (-4x25) + (2Fby)
Fby= 45 Newtons
Using ƩFy we get Fay= impossible!

Now if take the moment about point B i get
ƩMb=0
= (4x5)+(-2x25)+2Fay
Fay = 15kN
Using ƩFy we get Fby=15Kn
Can someone tell me where i went wrong please?? I just don't get it
 
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Spakfilla said:
View attachment 45438

Homework Statement


Find the Fay this is static equilibrium so ƩF=0 and ƩM=0

Homework Equations



ƩMa=0
= 2x5 + (-4x25) + (2Fby)
Fby= 45 Newtons
Using ƩFy we get Fay= impossible!
not impossible, you get a negative value for Fay; what does that imply about the direction of Fay?
Now if take the moment about point B i get
ƩMb=0
= (4x5)+(-2x25)+2Fay
Fay = 15kN
what is its direction?
Using ƩFy we get Fby=15Kn
No, watch plus and minus signs and their meaning.
 
Thanks so much I now see my mistake. Got the directions mixed up! Damn got to be more careful
 

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