Does a force create a moment about a point if the point is on the force's line of action?

[a1234]

Homework Statement

I'm a bit confused on when a force creates a moment about a point, and when it does not. In particular, in the attached diagram, would F be able to produce a moment about point A? I initially thought that wouldn't be possible as A lies on the same line as F, but since F does not seem to pass directly through A, I'm not so sure.

 

[FactChecker]

The force, F, alone does not produce torque at A. The fact that there is an offset stationary pivot point, O, means that there is a force at O opposing F which produces a torque around A. (You can see that if the pivot point, O was moved to the other side of the force at A, then the torque would switch to the opposite sign. So it is the opposing force at O that is controlling the torque.)

 

[PhanthomJay]

Note that the line of action of F does pass through A. A is the point or hole where the rod meets the bar. 3D drawings can get very confusing.