Moment is a physical quantity, which is used to measure the rotating effect of force on an object. It can be divided into the moment of force to point and the moment of force to shaft. The moment of a force to a point is a physical quantity, which is used to measure the rotation effect of a force on an object around that point.
The moment of force F to point O is defined as: the vector product of the vector diameter r of point A of force F relative to point O and force F is represented by M0(F), where M0(F)=r×F, and the moment of force to point is a vector whose magnitude is equal to the product of the magnitude of f and the vertical distance d (called the force arm) of the action line from point O to f, or equal to the area rFsinα of a parallelogram with R and F as adjacent sides. The direction of M0(F) is perpendicular to the plane formed by R and F, and R, F and m(F) satisfy the right-handed spiral relationship. A moment pointing to a point can be defined as any point in space. Because the moment of a force to a point depends on the position vector diameter r of the point of force action, the moment of the same force to different points in space is different. When the line of action of a force passes through a certain point in space, the moment of the force at that point is zero. If there are several * * * point forces (the point of action is a) fi (I = 1, 2, ..., n) acting on an object, and the resultant force F = F 1+F2+...+FN, then the moment M0 (f) of the resultant force to point O is equal to r × (f6544). Vector M0(F) is called the principal moment of this force system to point O.