Dropping a horizontal disk into a cylinder

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• Let us drop a light disk into a cylinder. As shown in this video, a 1-mm-thick styrene foam board is used (if unavailable, even ordinary paper can be used). This is cut into a circular shape slightly smaller than the diameter of the cylinder.
• Level the disk and gently release it into the cylinder. The disk slowly falls through the cylinder while staying horizontal. The level is stable.
• Air from the bottom flows through the gap between the disk and the cylinder; however, because the gap is narrow, the air passes slowly via a viscous action, which is why the disk falls slowly.
• Two disks can also be dropped in sequence, and they will fall slowly in the same manner.
• Next, cut a tissue paper into a circular shape and perform the experiment. Please cut the tissue paper carefully so it does not wrinkle. It also falls slowly without breaking.

[Keywords]	Viscosity, Air resistance
[Related items]	Slowly Dropping Ball, Dropping a slanting disk into a cylinder
[Reference]	“The Wonders of Flow”, Japan Society of Mechanical Engineering, Kodansha Blue Backs, P19.

Next　▶