Question

If block D weighs 300 lb and block B weighs 275 lb determine the required weight of block C and the angle theta for equilibrium?

Answer 1

set up a free body diagram.

and by reason, Tcd = Tbd

Tbd y = 275 - 300*sinθ
Tcd y = Tc - 300*sin30

Tbd x = 300*cosθ
Tcdx = 300 * cos30

Tbd^2 = (275 - 300*sinθ)^2 + (300*cosθ)^2
Tcd^2 = (300*sin30)^2 + (300 * cos30)^2

(275 - 300*sinθ)^2 + (300*cosθ)^2 = (300*sin30)^2 + (300 * cos30)^2
etc.