Negative or positive in rolling?

[uriwolln]

When, let's say, a cylinder is rolling on a plane, and there is a rope coiled around the cylinder and the rope moves at an acceleration of A(rope) at the upper part of the cylinder to the right.
Ok, so when I try to envision it, the cylinder is rolling in the CW direction.
so R(alpha)= - A(cylinder). When the acceleration of the cylinder is relative to the ground.
but then I need to look at the spring too, right?
so since the cylinder is STILL moving in CW direction, the equation for that should be
R(alpha)= - (A(cylinder) - A(rope))
But in questions I tired to solve they took it as positive.
Am I overlooking sth?

 

[JaredJames]

You have a cylinder and rope and then suddenly a spring?

What's R(alpha)?

Do you have a diagram? Either I'm missing something or this is a rather confusing description.

 

[uriwolln]

lets say to inorder for sth to roll you need to have the equation V=wR
so when you derive it, it goes a=alpha x R.
here is the diagram, there are no springs here.
http://img651.imageshack.us/img651/4328/setuppp.jpg

 

[rcgldr]

For the center of mass of the cylinder a = -alpha x R. Assuming the cylinder is rolling and not slipping, the string acclerates at twice that speed. This is assuming that alpha being clockwise is a negative number, and assuming you want left to right movement to be considered as positive.

 

[uriwolln]

ok, so let me get this straight.
because the movement if from left to right, then does the equation necessarily imply
a(rope) - a (cylinder)= -r x alpha.
the negative sign again here because the cylinder rolls in CW direction.
I mean, do I always get to do, the positive acceleration - which in this case is the rope- minus the other one?