p13_062.pdf

62. Since GA exerts a leftward force T at the corner A , then (by equilibrium of horizontal forces at that

point) the force F diag in CA must be pulling with magnitude

F diag =

sin45 ◦

= T √ 2 .

This analysis applies equally well to the force in DB . And these diagonal bars are pulling on the bottom

horizontal bar exactly as they do to the top bar, so the bottom bar is the “mirror image” of the top one

(it is also under tension T ). Since the ﬁgure is symmetrical (except for the presence of the turnbuckle)

under 90 ◦ rotations, we conclude that the side bars also are under tension T (a conclusion that also

follows from considering the vertical components of the pull exerted at the corners by the diagonal bars).