This video explains the general approach for internal forces on the beam.
At the beginning, the positive and negative cut faces are shown.
This is followed by the determination of the shear forces at the start and end of the beam.
This illustrates how important it is to have knowledge about the cut face.
In the positive side of the section, the axial force and the shear force point in the direction of the coordinate system. The moment points counterclockwise.
In a clockwise direction, these internal forces point to the negative side of the section.
In this case, the positive side of the section is the section of the component that is seen when the component is viewed from left to right.
For the negative side of the section, you cut from the right support or, in other words, from right to left.
This allows you to draw the shear force distribution very quickly.