Hello can someone please tell me if my preception is correct. Looking at the picture of a cantilever beam, the moment that is in blue is a reaction moment.
But, is it also the bending moment?
If not can you please explain to me the difference between the reaction moments and bending moments.
Thank you.
the moment of the force is not shown. But it is equal and opposite to the reaction.
Basically it is the result of
$$ \sigma M_{support}=0\ M_{reaction}+M{beam}=0$$
$$M{reaction}=-FL$$
In general, both moments are called the "bending moment", but you can distinguish them by looking at the member's face - when the force has a direct effect on it, it is the $M_{apply}$; the opposite is the $M_{react}$.
Another way to look it is - when the moment tends to bend the beam segment down (or up) in the same direction as the applied force, it is $M_{apply}$. On the other hand, $M_{react}$ tends to bend/pull the displaced segment back towards the original position.
The blue M is a reaction moment and a bending moment.
Essentially, M is the reaction required from the support in order to keep the structure from rotating (and moving) because of force F.
However the structure (in this case the beam) has to transfer somehow that reaction. (The way I think of it), is that at every cross-section of the beam you need to develop a "reaction" bending moment so that the structure will not rotate.
