Home > Activity > Enjoy Fluid Experiments Lab. > Remove a ball from a deep location 2

Remove a ball from a deep location 2

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

  • Let's remove the ball from a deep tube with the wind from a hair dryer. A 5-cm-diameter polystyrene foam ball is prepared. The tube diameter (inner diameter) is 6.3 cm, and the depth is 50 cm.
  • Even if the wind is blown with a hair dryer, it does not come out well. This is because the wind doesn't reach the bottom.
  • The pressure is low near the center of the vortex and high on the outside. This is due to the action of Centrifugal Force . Even on the upper side of the ball, the pressure is low near the center and high on the outside. The pressure on the underside of the ball is almost the same as the high pressure on the outside of the vortex, and the pressure difference between the top and bottom of the ball causes the ball to float. The egg-shaped polystyrene foam can be removed in the same way.
[Caution] "Centrifugal Force " is an apparent force that does not actually exist. When observing the phenomenon on a rotating object (rotating system), it can be considered that the centrifugal force is apparently applied. Here, it is explained that the air is pushed outward by the centrifugal force, and the pressure becomes higher toward the outside (the pressure distribution is the same in the stationary coordinate system and the rotating system).
[Keywords] Vortex, pressure
[Related items] Remove a ball or egg from the tube, Centrifuge, Remove a ball from a deep location 1

“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, P52-61

◀ Back Next ▶

Last Update:3.3.2017