Which force component is $F_{N3}$ on figure (2)?

Question

Here's a diagram of a man standing on a ladder that's currently fixed in position.

Forces are in equilibrium, and the ladder is static. There are two figures illustrating the forces acting on the ladder:

Fm and Fg are downward forces created due to the weight of the man and the ladder, respectively. FN1 and FN2 are the normal forces acting on the ladder from the wall and the ground. Ff is the frictional force acting on the ladder from the ground. On figure (2), there is another force, FN3, vertically acting from the wall to the ladder. Can this be considered as the frictional force acting on the ladder from the wall? Apparently the force is marked as another normal force, not frictional.

Answer 1

Imagine that the floor was frictionless. That is, $F_f=0$. If there was also no frictional force between the wall and ladder, the ladder and man would fall to the ground.

This means that $F_{N3}$ is a frictional force. The ladder is pushing against the wall at the top point, so there is a normal force perpendicular to the wall called $F_{N1}$. Since there is friction between the wall and ladder, $F_{N3}$ acts to stop the ladder from slipping and falling (as does the other frictional force $F_{f}$ which acts horizontally). This is why $F_{N3}$ points vertically upward.

Remember that in such situations, normal forces and frictional forces are always perpendicular to each other. In the diagram you have the normal force $F_{N1}$ which is at $90^\circ$ to the wall, and so $F_{N3}$ which is perpendicular to that, should be a frictional force.