.....as a concept , at : www.thingiverse.com/thing:516978 (http://www.thingiverse.com/thing:516978)
A free gravity fall is a straight line.
A free rotational " fall " is a spiral .
The one and the other are " natural " motions...
For the present moment , we have an application to increase the momentum of small size particles :
www.wikipediatldr.com/articles/402809/cyclotron
Al_ex