Just as force has a tendency to translate the body, moment has a tendency to rotate the body about the point.
Our sign convention will be as follows. If the force has tendency to rotate the body in counterclockwise sense, moment is considered +ve. If the force has tendency to rotate the body in clockwise sense ,moment is considered -ve.
A convenient way to find out the direction of moment is as follows. Imagine to stand on the line of action of force , facing yourself in the direction of arrow. If the point O (about which moment is desired) is towards your left, moment is positive. If the point is towards your right , moment is negative.
| Fundamentals of Engineering Mechanics |
Moment: The moment of a force about a point O is the cross product of r and F, where r is the position vector of any point on the line of action of force with respect to O. M = r × F |