Ultracentrifuge

a special centrifuge machine that generates high centrifugal forces as it is capable of spinning at speeds up to 50,000 revolutions per minute. The ultracentrifuge is most commonly used during the separation of the various ORGANELLES within cells. The larger and more dense organelles will form a deposit in the centrifuge tube more readily than the smaller, less dense ones. The nucleus is the largest organelle of any normal cell and will be deposited at the bottom of a centrifuge tube when the ultracentrifuge spins at a force of 600g for 10 minutes, whereas the smaller MITOCHONDRION needs a higher speed of 15,000 g for 5 minutes to be deposited.

Taken from Dictionary of Science