Mechanics of Materials - Where's my mistake?

[I like Serena]

Hi I am the friend, just to confirm:

A= π/4*(D)^2-π/4*(D-2α)^2

Yep. That is the proper formula for the area of the cross section.

 

[niece of md.]

Thanks I'll change that, but I am allowed to make those mistakes since I don't really study it, I just do it for fun :)

 

[I like Serena]

Well, I'm just doing this for fun too.
But I don't allow myself many mistakes! ;)

 

[Femme_physics]

Well, I do it for fun and for a degree! Thanks for helping out ILS we got it done, and are off to solve more complicated stuff now. Hopefully it'll go more smoothly.

 

[niece of md.]

I was trying to solve this exercise but since it's in English I wasn't sure I understood it.

this is what I did:

I was a little confused with +/- sings on F(bc).

 

[I like Serena]

The signs appear to have been no problem at all and your work is neat!
I give it the ILSe Seal of Approval!