I was watching a video about torque in which the task was to find the force $F_2 $ when a body is in equilibrium. The person in the video said that in order for the body to be in equilibrium, two things must happen: a) the net force must be zero, and b) the net torque must be zero.
Now, when solving the problem, he wrote that
net force = force $F_1$ + force $F_2$ + force of reaction ($F_1$ and $F_2$ were forces acting on the body)
net torque = torque1 + torque2 + torque of the reaction force
Investigating a bit more, I learned that there are two types of equilibrium: translational and rotational. In the video they didn't specify which one they meant, but I'm guessing it was both since we're taking both net force and net torque into account.
What I don't understand is why the reaction force is used here. I thought that translational equilibrium happened only when the net force ACTING ON a body is zero. But the reaction force is not a force acting on the body, it's a force being exerted by the body. In the same way, rotational equilibrium is when the net torque acting on the body is zero.
So why is the reaction force relevant? Is the person in the video wrong, or should we use the reaction force for calculating the net force and net torque? This was the situation presented:
According to my interpretation, it's not possible for that object to be both in translational and rotational equilibrium at the same time.