Ok, i've been looking around for a answer for this , but havent found one. So in hope for some help, ill post the problem here: A pipe has the form as a half cylinder. On the top of the cylinder its placed a item that can slide frictionfree on the cylinder. The cylinder gets a microsmal puff, so the system starts. What angel does the radius make with the horizontal axis in the moment the item loses its contact with the cylindersurface? Any help solving this would be of great appreciaton from me :shy: I've tried attacking this with finding an expression for the angle, but it failed. Im having problems realy understanding whats causing the item to lose the surfacecontact with the cylinder. Im sure it has something to do with the speed of the item , combined with the angle for the position... im realy drawing a blank here.