Internal Forces (Engineering Mechanics)

[physicsss]

problem says knowing radius of each pulley to be 7.2 in, neglect friction, find internal forces at point J of the frame.

1st question that I have is whether the tension in section C-E of the cable also 90 lb? how about section C-D. Also, in my diagram of each of the members, I don't know how to label forces at point E where two long members and the pulley meet.

Finally, can someone gimme an idea how to go about doing this problem?
http://img487.imageshack.us/img487/8272/15am.jpg
http://img487.imageshack.us/img487/4066/14ch.jpg

[Pyrrhus]

Are points J and K joints? I think they are assuming pulleys have mass.

[physicsss]

They are not joints. You're supposed to cut the member along that point to find the internal forces.
it's kind of like this: https://ecourses.ou.edu/cgi-bin/ebook.cgi?doc=&topic=st&chap_sec=08.1&page=theory&appendix=0

[Pyrrhus]

Yes, i'm familiar with internal forces [resultants of the stresses] (axial, shear and flexionant moment). First is to find the reactions and simply cut BE member at J, and solve for the shear force and flexionant moment.

[HeartbreakidX]

I beleive you dont need to take pulleys into consideration you just find all the force around the member where point J is.
Then you just cut at point J and calculate everything again

[physicsss]

I'm having trouble finding the vertical component of the force acting on frame B...any ideas? I set the moment about A zero and I was able to find the horizontal component of the force acting on frame B.

[Pyrrhus]

Find the joint forces (E point) on the AE member then use them to find the vertical component of the reaction at B on the BE member.

[physicsss]

I got 45 lb for the vertical component of the reaction force. is that right? :confused: