Search
 
 

STATICS - THEORY

    The Moment Vector


Moment Vector


Effect of Force Angle

 

The moment about a point in 3-D space can be determined from the same basic scalar equation as in previous section on 2D scalar moments.

     Mo = r F

Here F is the magnitude of the force, and r is the perpendicular distance to the line of action of the force.

A force acting on a body in 3-D space tries to rotate the body in a plane defined by the force's line of action and the point under consideration. Since this plane is often difficult to visualize or define, a double-headed vector is used to define the axis about which the force is tending to rotate the body. The magnitude of the vector is the magnitude of the moment generated by the force.

The moment of a force in 3-D space can also be calculated using the Principle of Moments discussed in in the previous section. However, as it was seen, determining angles and distances in 3-D space can be very difficult. The next section will introduce a vector approach to calculating moments that greatly simplifies the process and reduces the number of steps necessary in calculating a moment vector.

     

Right Hand Rule
 
Moment vs Actual Rotation
     
   
 
Practice Homework and Test problems now available in the 'Eng Statics' mobile app
Includes over 500 free problems with complete detailed solutions.
Available at the Google Play Store and Apple App Store.