If you have a very thin glass tube and you place it into water, let's say the water in the tube rises to the height of $x$ mm from the surface of the water. What would happen if you poked a hole in the tube at a height $n$ where $n<x$ and coated the sides of the hole with hydrophobic material so water could more easily slip through it. Wouldn't the water just cascade outward? And then the capillary action of the water would pull up more water, causing, in my mind, a perpetual motion machine? Energy conservation is raising its eyebrows at me now but doesn't offer me any help. Please evaluate this scenario and show me why it can't happen.
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The second law is the definition of temperature and you didn't mention temperature anywhere in your question, so obviously it can't apply. What does apply is simple energy conservation. – CuriousOne Jun 08 '15 at 15:39
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@CuriousOne :P My bad again, I'll edit that. – HyperLuminal Jun 08 '15 at 15:41
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@HyperLuminal : More on capillary-action and perpetual motion. – Qmechanic Jun 08 '15 at 16:05
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http://physics.stackexchange.com/q/89223/8851 "How is the water meniscus at the edge of a capillary tube", http://physics.stackexchange.com/q/88544/8851 "Capillary tube of insufficient length" may be more relevant. It deals not with the case of a hole on the tube, but with a shorter tube, but that's close enough. – b_jonas Jun 08 '15 at 16:56
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As soon as you make a hole one of two things will happen:
- If the diameter of the hole is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and adhesive forces between the liquid and container act to seal the hole.
- If the hole is large enough so that water can leak, then the height of the water column will lower to equal the pressures. Remember that the pressure inside the water column in larger that the atmospheric pressure.
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