Gaining a Benefit Behind a Large Object

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What type of experiment is this?

Experimental procedure and explanation:

• When a flat board or quadrangular prism is placed in air flow, separation occurs and a circulating flow is produced behind the object.
• When another object is placed behind the flat board or quadrangular prism, the object will move toward the board or the prism due to the circulating flow.
• In a marathon or an automotive road race, this principle can be used to decrease air resistance and thereby reduce energy consumption. Therefore, in order to preserve energy, a strategy is used in which a runner or a race car driver travels directly behind the lead runner or driver rather than positioning himself at the front.
• Moreover, in this experiment, when the front object is large enough, in addition to a reduction in air resistance, a propulsive force (a force that pushes an object forward) may act on the trailing object in some cases.

[Keywords]	separation, air resistance
[Related items]	Quickly Dropping Light Objects, Air Flow Behind a Board
[Reference]	he Japan Society of Mechanical Engineers, “The Wonders of Flow (Nagare no Fushigi),” Kodansha Blue Backs, pp. 136–139. Ryozo Ishiwata, “Illustrated Fluid Dynamics Trivia (Zukai Zatsugaku Ryutai Rikigaku),” Natsume Publishing, pp. 66–69, pp. 164–165.