When two table tennis balls are suspended from a support by thin strings and air is blown between them, a few key physical principles come into play, primarily related to fluid dynamics and forces acting on the balls. Here's what happens:
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Introduction of Airflow: When air is blown between the two suspended table tennis balls, a stream of air flows into the space separating them.
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Bernoulli’s Principle: According to Bernoulli's principle, when the velocity of a fluid (in this case, air) increases, the pressure within that fluid decreases. As the air is blown between the two balls, it moves faster in that region compared to the surrounding air. This creates a lower pressure zone between the balls.
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Pressure Difference: Due to the lower pressure region created by the fast-moving air in between the balls, there is a pressure difference between the outside air (higher pressure) and the air flowing between the balls (lower pressure). This pressure difference can exert an upward force on the balls.
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Attraction of the Balls: As a result of this pressure difference, the two table tennis balls will move towards each other. This occurs because the higher pressure surrounding the balls acts to push them together while the lower pressure in the center acts to create a "suction" effect that pulls them closer.
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Equilibrium: If the airflow is steady and sufficient, the two balls may come very close together or even touch, depending on the strength of the air pressure and the distance between the balls when the air is blown. They will generally remain suspended as long as there is continuous airflow, maintaining a stable position dictated by the balance of forces.
This phenomenon demonstrates principles of fluid dynamics and is a visual representation of how pressure differentials can lead to movement in objects. It can also serve as a simplified illustration of concepts like the Coanda effect, where fluids tend to follow nearby surfaces, contributing to the dynamic behavior observed in this scenario.