A centrifuge rotor holds sample vessels around the rotation axis. A fixed-angle centrifuge rotor holds tubes at a fixed inclination; a swinging-bucket centrifuge rotor lets them swing outward during rotation. Material moves away from the axis, so a centrifugation pellet can first collect against an outer tube wall rather than travel along the entire tube axis. Geometry sets both the rotor radius and the travel distance.[ref]
Basics: Centrifugal Force & Centrifuge Type by Eppendorf. Basics: Centrifugal Force & Centrifuge Type, Fixed-angle or swing-bucket rotors? and Fixed-angle rotor: tube orientation and pellet position
New to topics? Read the docs here!