Why Is Tension Zero at the Free End of a Rotating Rope?

[andyrk]

A rope is tied at one end then rotated in a vertical circle. Why do we take the tension at the free end of the rope as 0(Boundary Condition)?

 

[berkeman]

A rope is tied at one end then rotated in a vertical circle. Why do we take the tension at the free end of the rope as 0(Boundary Condition)?

What is the end of the rope pulling on?

 

[andyrk]

Nothing, so this is a silly doubt then I guess but for tension to occur there should be actual contact present between the string and some other object, right? Which in this case is missing from the free end of the rope?