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Turn with a stream of water

Experimental procedure and explanation:

• Make a spinning toy that takes advantage of the flow of water.
• First, make a turntable. Stack the plastic bottle caps as two layers. Put the hole through the center (it is good to drill with a pin vise, etc.). Attach the shaft (toothpick or bamboo skewer) to the pulley (which may be another round plate). Insert a bead to make it easier to rotate, and insert this shaft into the hole in the cap.
• Next, create a vane wheel. Cut out a disk from a juice or milk box (5 cm in diameter in this video). Paper cartons work well because they do not easily get wet. Cut out the circumference of the disk as shown in the figure. Then, do a valley fold along the red lines in the figure and paste it on the turntable.
• Pour water from the tap so that it hits in the middle of the vane wheel. The water spreads outward, hits the blades, turns, and flows out. A force acts on the blades in the direction opposite to the direction in which water comes out (called action / reaction) to rotate the vane wheel (called moment of force).
• Change the shape, size, and folding of the blades to see how they turn and how the water moves.
• It can be dangerous to do handicrafts, so let's do this with an adult.
• Water is an important resource. Be careful not to waste water.
 [Keywords] Angular momentum theory [Related items] Water flower, Sprinkler [Reference] “The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, P114-117“Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natsume Publishing, P170-173
Last Update：3.3.2017