Which description matches swing-out centrifuge operation?

• A. The tubes are fixed and do not move
• B. Tube buckets start vertical but then spin out to horizontal
• C. The rotor always remains upright
• D. The samples must be pre-treated before spinning

Answer: (B)

In swing-out centrifuge operation, the tube holders are mounted on pivots so they swing outward as the rotor spins. When the rotor is stationary, the tubes hang vertically. As speed increases, centrifugal force causes the holders to swing from vertical toward a horizontal orientation, so the tubes end up side-by-side in a near-horizontal plane. This change in orientation can improve separation by positioning the sediment along the bottom of the tube and making it easier to observe and re-suspend the pellet. The description fits swing-out rotors, unlike fixed-angle rotors where tubes stay at a fixed tilt, or statements implying the rotor itself remains upright or that pre-treatment is required.