Answer
$F = 200~N$
Work Step by Step
If the system is in equilibrium, the torque exerted by the applied force $F$ about the support must be equal in magnitude to the torque exerted by the weight about the support.
We can find the applied force $F$:
$r~F = r_w~mg$
$F = \frac{r_w~mg}{r}$
$F = \frac{(0.50~m)(1200~N)}{3.0~m}$
$F = 200~N$
