6. Replace the \( 12-\mathrm{kN} \) force acting at point A by a force-couple system at (a) point O and (b) point B .
7. The cantilevered beam shown is subjected to an 8 kN force F applied by means of a welded plate at A . Determine the equivalent force-couple system at the centroid of the beam cross section at the cantilever O.
8. If the resultant of the forces shown passes through point A , determine the magnitude of the unknown tension \( T_{2} \) which acts on the braked pulley.