0:00
Okay, so we have this trust.
00:01
We want to find the forces in these three members, b, c, hc, and fg, using the method of sections.
00:10
The first step in the method of sections is to treat the trust as an entire and just figure out the forces at each end.
00:23
So i drew the applied forces in red.
00:25
The ones we want to calculate right now are these.
00:31
I'm going to call them f1 and f2.
00:34
Those are the only forces of support.
00:38
There's no horizontal force at a.
00:43
Actually, it's called these f -a and f -b.
00:49
All right.
00:53
And of course, each of these distances is faa.
01:05
All right.
01:06
So we got in the y direction.
01:20
So that tells us that, all right.
01:32
Well, actually, it's 20 kiloton.
01:40
Then i'll construct a moment equation.
01:46
I'm going to choose a is my center.
01:49
So we got it.
02:50
So now the next step is go back to our original truss.
02:55
And we're going to cut it like this...