I'm doing a problem on static equilibrium and I'm unclear whether a force exists or not. This is my force diagram:
The setup is: a homogenous rod with a certain mass is attached to a vertical wall on one side, an object hangs on the other side, and a cable connects the rod to the wall with a tension T. I understand which forces are needed for static equilibrium. What I'm confused about is what's happening at point A. Since the wall exerts a force on the rod which points upwards (Fy, rod), per Newton's 3rd Law does the rod then exert a force on the wall which points downwards (Fy, wall)?
Best Answer
You can simplify your force diagram by highlighting forces that is more important. On the horizontal component, you have $T_x$ from the rod acting to the wall, thus the wall also exert an equal force to the rod $F_{x,wall}=-T_x$. The force acting upwards that you described is better perceive as the (static) friction force. Now the vertical force component is balanced by force acting upwards against force against downwards. So, you can write it as $F_y+T_y = -(F_1+F_2)$. Here you already established the force equilibrium. You can further solve this by incorporating equilibrium in the moment to the equation too.