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I have a question regarding tension in a rope. Consider a situation where two masses $A$ and $B$ are tied by a massless string on a horizontal plane with no friction.
Suppose we pull mass $A$ by a force $F$ then the string exerts a backward force on the block; assume $T$. An equal amount of force is applied by the block on the string, which pulls the Block $B$ with force $T$. The Block $B$ exerts a force backward on the string with magnitude $T$.
So far the argument seems good, but why do we stop here? This backward force again pulls $A$ backward by the string. The string is again pulled forward by $A$ by Newton's Third Law, which again results in the same process...Thus there are forces acting in infinite directionsbetween the boxes..?
Where is the problem in the argument?