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The two-balloon experiment is a simple experiment involving interconnected balloons. It is used in physics classes as a demonstration of elasticity. Two identical balloons are inflated to different diameters and connected by means of a tube. The flow of air through the tube is controlled by a valve or clamp. The clamp is then released, allowing air to flow between the balloons. For many starting conditions, the smaller balloon then gets smaller and the balloon with the larger diameter inflates even more. This result is surprising, since most people assume that the two balloons will have equal sizes after exchanging air. The behavior of the balloons in the two-balloon experiment was first explained theoretically by David Merritt and Fred Weinhaus in 1978. ==Theoretical pressure curve== The key to understanding the behavior of the balloons is understanding how the pressure inside a balloon varies with the balloon's diameter. The simplest way to do this is to imagine that the balloon is made up of a large number of small rubber patches, and to analyze how the size of a patch is affected by the force acting on it.〔 The James-Guth stress-strain relation 〔 〕 for a parallelepiped of ideal rubber can be written : Integrating the internal air pressure over one hemisphere of the balloon then gives : where ''r''0 is the balloon's uninflated radius. This equation is plotted in the figure at left. The internal pressure ''P'' reaches a maximum for : and drops to zero as ''r'' increases. This behavior is well known to anyone who has blown up a balloon: a large force is required at the start, but after the balloon expands (to a radius larger than ''r''p), less force is needed for continued inflation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Two-balloon experiment」の詳細全文を読む スポンサード リンク
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