Line of action

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For the board game, see Lines of action.

In physics, the line of action of a force F expresses the geometry of how F is applied. It is the line through the point at which F is applied and along the direction in which F is applied.[1]

The concept is essential, for instance, for understanding the net effect of multiple forces applied to a body. As an example, if two forces of equal magnitude act upon a rigid body along the same line of action but in opposite directions, then they have no net effect—loosely speaking, they cancel one another out. But if, instead, their lines of action are not identical, but merely parallel, then their effect is to create a moment on the body, which tends to rotate it.

Line of Action plays an important role in constructing human figure in a more convincing action pose. It is an imaginary line extending through the main action of the figure. Plan Your Figure and details to accentuate the line.

One practical application of the concept is in animation and character posing.


  1. ^ *Kane, Thomas R.; Levinson, David A. (1985), Dynamics: Theory and Application, McGraw-Hill Series in Mechanical Engineering, McGraw-Hill, Inc., ISBN 0-07-037846-0