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Remove a ball or egg from the tube

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What type of experiment is this?

Experimental procedure and explanation:

  • Use a hair dryer to remove the ball and egg from the tube. The polystyrene foam ball has a diameter of 6 cm, and the egg has a diameter of 5 cm. The tube diameter (inner diameter) is 6.3 cm. If it's too deep, the objects won't come out well, so a base was placed inside the tube.
  • The ball could be removed by blowing the wind toward the center of the ball. The principle is the same as "Float an egg". The pressure increases where it hits the center of the ball, but then it also increases where the air flows along the ball and then turns around, and the force from this pressure is greater than the force of the flow that hits the center of the ball. The pressure on the underside of the ball is approximately the same as the pressure at this turning point. The pressure on the underside generated a force that pushed upward, which was stronger than the force pushing downward, causing the ball to lift.
  • In this experiment, the center of the ball was the target, but there is also a method of letting air flow along the wall of the tube (Removing a Ball from a Cylinder).
  • Even an egg-shaped object can be removed using the same principle.
[Keywords] Momentum theory, pressure
[Related items] Float an egg, Removing a Ball from a Cylinder, Force When Flow is Pushed Back

“Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natsume Publishing, P200-201

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Last Update:3.3.2017