Please see my attachment
In the diagram, F1 and F2 are equal and opposite also F3 and F4 also equal and opposite.
Its been mentioned that F1 and F2 have same line of action of force and the resultant effect on the loop is zero. But F2 and F4 have different line of action and hence constitute a couple.
The Attempt at a Solution
I have drawn lines of action for F1 and F2, F2 and F4 in dotted line in red colours. I cant find any difference between F1 and F2 , F2 and F4. Both are straight lines. So in what way the lines of action of F2 and F4 are different and how do they constitute a couple?
2) What is the rule that i has to apply to find the direction of force, in this case?
I mean why all the forces are directed outwards to the loop?
Thanks in advance revered members