In these steps you model a 2D curtain rod from a plane and attach hair to it. Then you add and keyframe a sphere in the scene to later be used as a collision object.
To create the curtain using Hair
(If you have previously shut off the interactive primitive creation option, simply click once in the scene to create the primitive at the origin.)
Hair is created and attached to the plane.
The sphere passes through the curtain as though the curtain weren’t there. In the next steps you set the sphere as a collision object with the hair.