Moment of a Force about a Point
This Demonstration shows how to find the torque, or moment of force, exerted by a rope on a boom about the point . The torque is a vector quantity, usually written . You can vary the force and the distance . When distance is expressed in meters (m) and force in newtons (N), the torque or moment has the dimension newton-meters (Nm).[more]
To find the moment about , multiply the magnitude with the unit vector from to . Next, use the position vector from to the tension . Finally, the torque about is given by the cross product[less]
 F. P. Beer Jr., E. R. Johnston, E. R. Eisenberg, W. E. Clausen, and G. H. Staab, Vector Mechanics for Engineers: Statics and Dynamics, 7th ed., Boston: McGraw Hill, 2003.