what do you do next?

And so what you should do at this point is

do another drawing cut or section cut to continue to solve.

we'll do a joint cut at point P2.

And if I draw that free body diagram, I've got my 1,400 pound force

up and to the right. I have the 900 pound force down.

I have two components of my cut between P1 and

P2, I've got an x component and a y component.

I know that the x component, again, is the same throughout.

Because there's only, there's no external forces in the x direction.

So, I know right away.

That T12 in the x direction is a 1109.9 pounds, and so I can take that joint

cut now, and all I have to do is find the T12

in the y direction, its y component. So, to do that what should you

do? Okay and so what, what you

should have said is, okay I can just sum forces

in the Y direction so that it will be equal to 0.

I will choose up as positive and so I get the T12

y component minus 900 plus the y component

of the 1,400 force, which is 1,400 times

sine of 37.56 degrees equals 0. And if

you solve for T12 Y now, you find

it's equal to 46.67

pounds. So now I have T12 x component

and y component. I can use Pythagorean's theorem to sum

those up together. So T12 will be equal to

the square root of T12 X squared

plus T12 Y squared,

T12 X is 1109.9,

T12y we just found to be

46.67. So T12

overall is equal to 1111

pounds in tension.