Positive and negative relationship between force and moment in mechanics of materials How to judge the positive and negative of force, moment and bending moment when setting up the balance equation

Positive and negative relationship between force and moment in mechanics of materials How to judge the positive and negative of force, moment and bending moment when setting up the balance equation

The positive and negative of the force is related to the projection coordinate axis
The positive and negative of the moment can be defined by oneself when the balance equation is set up, and generally the counter clockwise is taken as the positive
The positive and negative of bending moment is related to deformation. For mechanical majors, bending moment is positive when bending deformation is concave upward; for architectural majors, it is opposite