Solució: \begin{align} ∑ FM = 0 &= \cssId{Step1}{F_C·sinφ·(L/2) + mg·(L/2) + F·(3L/2)} \\[3px] &\cssId{Step2}{F_C·sinφ·(L/2) = -mg·(L/2) - F·(3L/2)} \\[3px] &\cssId{Step3}{F_C = \frac{-mg·(L/2) - F·(3L/2)}{sinφ·(L/2)}} \\[3px] &\cssId{Step4}{NOTA:~La~gravetat~és~negativa} \\[3px] \end{align}