What is the line of action of force and how does it relate to torque?

[logearav]

Homework Statement

what is meant by line of action of force? how to understand this concept? suppose i kick a ball and the ball moves in east. then can i say the line of action of force is along the movement of the ball, that is towards the east. i find this concept of line of action of force in toque. could u please help me to understand, revered members?

Homework Equations

The Attempt at a Solution

 

[Gear.0]

You could think of the line of action as a sort of axis along which the force is applied.
Unlike the force vector which begins at the point where the force is applied and extends according to the magnitude of the force, the line of force goes through the point and extends indefinitely in both directions.

http://en.wikipedia.org/wiki/Line_of_action

It is a geometric construct. If the lines are not identical you will have a torque applied. Note that when they say identical in this case that includes position. Even if the lines are parallel but not identical then you will still have torque.