see here for a situation of the problem http://i40.tinypic.com/6fbblk.jpg
The Attempt at a Solution
Ok well I've solved this problem but one thing about the solution process troubles me.
Namely when trying to find the force in the bar.
Say for instance i have the acceleration of the block B.
I don't understand why i can't do a force balance such that,
-Mb*g -Tsin(a) = Mb * Ab (1),
instead the solution is
-Tsin(a) = Mb*Ab (2)
I don't understand why the weight of the object is not accounted for in equation 2. Can someone please clear this up for me, thanks!