Centrifuge

Let's take a look!

Watch the video on YouTube.

What kind of experiment is this?

Experimental procedure and explanation:

• When the basin is rotated, the water inside rotates with it, creating a forced vortex. Peripheral speed is proportional to the radius; the farther you move from the center, the faster the peripheral speed.
• Centrifugal forces acting on tea leaves are larger than those acting on water because tea leaves are heavier than water. Therefore, the rotation causes heavier objects to move farther from the center than lighter objects, and separation occurs. (In fluid dynamics, we often observe this phenomenon along with rotating fluid particles (a rotating coordinate system). With this in mind, and with the help of apparent and centrifugal forces, we will explain the current phenomenon.
• The faster you rotate the basin, the larger the forces and lesser the time taken for separation. This principle is exploited in using a centrifuge to separate substances.

(An explanation was added as Mr. Takuya Matsuda (honorary professor, Kobe University) pointed out that it was misleading.)

[Keywords]	forced vortex
[Related items]	Forced vortex, Centrifugal force
[Reference]	“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs pp. 52-59