Drawn in Spoon

Let's take a look!

Watch the video on YouTube.

What type of experiment is this?

Experimental procedure and explanation:

• Lightly grip the end of a spoon handle, and then cause the spoon to contact the flow of water. When this is done, the spoon is drawn into the flow.
• This is due to the Coanda effect. The flow of water bends to the right around the spoon’s curvature.
• At this time, a force directed to the right acts on the water flow, and as a counteraction, a force directed to the left acts on the spoon. Therefore, the spoon is drawn into the flow.
• Next, the same phenomenon occurred with a styrofoam ball.
• Even when the string is pulled to the right, the ball does not separate from the water flow. At this time, notice that the flow of water bends to the right. When the string is pulled strongly to the right, the flow bends further to the right. Moreover, when the force is weakened, the amount of bending is also weakened. Try it yourself.

[Attention]	It has been explained that “because the flow rate is higher at locations where the water is flowing than at locations where the air is stationary, the pressure becomes lower based on Bernoulli’s principle, and the surrounding objects are drawn in.” However, this explanation is incorrect. It is wrong to say that the pressure simply decreases because of the flow alone. At the location where the flow of water contacts the air, the pressure is equivalent to the atmospheric pressure. (For details, refer to the bibliography.) In this experiment, there is a significant bending of the water flow along a curved surface.
[Keywords]	Coanda effect
[Related items]	Flow Around the Back of a Cylinder, Circle and Square 1
[Reference]	Isao Imai, “Fluid Dynamics, Vol. I,” Shokabo, pp. 66-67. The Japan Society of Mechanical Engineers, “The Wonders of Flow (Nagare no Fushigi),” Kodansha Blue Backs, pp. 128-133. Ryozo Ishiwata, “Illustrated Fluid Dynamics Trivia (Zukai Zatsugaku Ryutai Rikigaku),” Natsume Publishing, pp. 214-215 and pp. 206-209.