I have difficulty knowing the direction of friction on static structures. The structure of the image is on equilibrium, and the exercise askes the maximum force P that the structure can take. Would friction force be to the right or left on point B ? why?
If the roll was free to rotate (without that tension), I think the friction force direction on B would depend of the application point of force P. Furthermore, on dynamics we can discover if our assumption is correct. Here in statics, to solve the problem correctly usually we have to take the correct directions of friction.
In this case, since force P is creating a positive moment, we would need something to cancel it, in order to be static. So, friction force would be to the left.
Is this the right thought? Or do I have to think what would be the direction of friction if that roll was free to rotate, and that would be the same direction to this problem?